This is a very rushed idea I've had (and I will likely edit it in the future)
Avanti West Coast:
xx:20 Manchester Picc (Milton Keynes, Stoke, Macclesfield, Stockport)
xx:23 Birmingham (Watford Jct, Rugby, Coventry, Bham Intl)
xx:30 Glasgow (Crewe, Warrington, Wigan, Preston, Lancaster, Oxenholme, Penrith, Carlisle)
xx:33 Liverpool Lime St (Stafford, Crewe, Runcorn)
xx:40 Manchester Picc (Crewe, Wilmslow, Stockport)
xx:43 Wolves (Milton Keynes, Coventry, Bham Intl, New St, Sandwell & Dudley)
• Chester/Holyhead services to start from Crewe.
• No services to Blackpool, Wrexham or Shrewsbury.
• No ticket inspections at Euston and early platform announcing for the safety of staff and to avoid the Euston scrum which causes crowds.
• All services out of Euston run with Pendolinos to avoid crowding.
LNWR/WMR:
xx:00 Northampton (Harrow, Bushey, Watford, Kings Langley, Apsley, Hemel, Berkhamsted, Tring, Bletchley, Milton Keynes, Wolverton)
xx:30 Northampton (Harrow, Watford, Kings Langley, Apsley, Hemel, Berkhamsted, Tring, Cheddington, Bletchley, Milton Keynes, Wolverton)
xx:45 Crewe (Milton Keynes, Rugby, Nuneaton, Atherstone, Tamworth, Lichfield, Rugeley, Stafford, Stone, Stoke, Kidsgrove, Alsager)
• Northampton services all run with 12 car 350s to avoid crowding.
• 2tph Northampton to Birmingham (all stops apart from alternating trains calling at Hampton in Arden and Adderley Park).
• 2tph Birmingham to Liverpool (all stops other than Acton Bridge).
• 2tph Birmingham to Rugeley via Aston (all stops).
• 2tph Cross City Line from Lichfield to Redditch (all stops).
• 1tph Birmingham to Shrewsbury (Sandwell & Dudley, Wolves, all stops)
• 1tph Birmingham to Hereford (normal calling pattern).
• All services run at max length to avoid overcrowding.
Caledonian Sleeper: Both cancelled.
Southern:
• All Gatwick Express services are cancelled (lack of demand to airport so these become unviable anyway).
• All WCML services cancelled.
• Dorking to Horsham to have no service with Victoria to Horsham services curtailed to Dorking.
• Peak time extensions to Guildford cancelled.
• London Bridge to Coulsdon Town services cancelled.
• London Bridge to Caterham via Streatham services cancelled.
• Peak extra services cancelled.
• London Bridge to Uckfield services to start from Oxted once the East Grinstead landslip has been sorted.
• Littlehampton to Portsmouth services cancelled with stops distributed to London/Brighton to Portsmouth/Southampton services.
• Brighton to Hove shuttles cancelled.
• Brighton to Lewes shuttles cancelled.
• Eastbourne to Ashford cut back to Hastings to Ashford with stops filled in by Brighton to Hastings services.
Thameslink:
• Luton to Rainham cancelled with stops that have no service due to this served by Southeastern services.
• Littlehampton and East Grinstead peak services cancelled.
• Peterborough to Horsham split to Peterborough to Kings Cross and London Bridge to Horsham.
• Cambridge to Brighton services cancelled with stops filled in by the Cambridge to Kings Cross and Bedford to Brighton services.
• Luton/Kentish Town to Orpington services start from Blackfriars.
• Planned additions to the service in the May timetable change to not take place due to the disruption.
Great Northern:
• Kings Cross to Ely services cancelled.
• All peak extra services cancelled.
• Moorgate to Welwyn and Hertford services halved to 2tph.
SWR:
• Waterloo to Poole stopping services to start at Southampton.
• Waterloo to Portsmouth via Eastleigh services to start at Eastleigh.
• Waterloo to Weymouth services to pick up any missed stops.
• Waterloo to Portsmouth fast services halved to 1tph.
• Waterloo to Portsmouth and Southsea stopper extended to Portsmouth Harbour.
• Waterloo to Haslemere services cancelled with missed stops picked up by the Portsmouth stopper.
• Waterloo to Salisbury services cancelled with missed stops picked up by the Exeter service.
• No services from Waterloo to Bristol.
• Waterloo to Weybridge services reduced to a Virginia Water to Weybridge shuttle that connects to Reading services.
• Hounslow loop services to only run Waterloo to Hounslow via Isleworth.
• Peak extra services cancelled.
• Waterloo to Dorking/Guildford via Epsom cancelled with services only running 2tph Waterloo to Epsom.
• Waterloo to Shepperton services start at Kingston with connections to Waterloo loop services.
• Waterloo to Woking and Basingstoke services combined, calling at Vauxhall, Clapham Jct, Earlsfield, Wimbledon, Surbiton then all stops all the way to Basingstoke.
Crosscountry:
• Manchester to Bristol (everything NW to SW) services cancelled.
• Newcastle to Reading (everything NE to SE) services cancelled.
• Everything terminates at Plymouth, extensions to Penzance and Paignton cancelled.
• Everything terminates at Edinburgh, extensions to Aberdeen, Dundee and Glasgow cancelled.
• All services to run with double Voyagers or HSTs to stop crowding.
• Birmingham to Nottingham service cancelled.
• Birmingham to Stansted service terminates at Cambridge.
• Birmingham to Leicester service cancelled with missed stops covered by the Cambridge service.
•
EMR:
xx:00 St Pancras to Sheffield (Leicester, Loughborough, Long Eaton, Derby, Chesterfield)
xx:30 St Pancras to Nottingham (Bedford, Wellingborough, Kettering, Market Harborough, Leicester, Loughborough, Beeston)
• 1tph Kettering to Corby shuttle that connects with the London service.
• Mansfield to Nottingham services cancelled.
• Liverpool to Norwich services start at Manchester Piccadilly.
• Terminate Matlock to Newark at Nottingham, with missed stops covered by Leicester to Lincoln.
TPE:
• Liverpool to Scarborough to only run from York to Scarborough.
• Manchester to Redcar to only run from York to Middlesbrough.
• Manchester Airport to Newcastle to start at Piccadilly main shed and not go through the Castlefield corridor.
• All services terminate at Newcastle with no Edinburgh extensions.
• Manchester Airport to Cleethorpes to start at Manchester Piccadilly.
• Irregular Liverpool to Glasgow services cancelled.
Heathrow Express: All services cancelled.
London Overground:
• Richmond to Stratford 2tph.
• Clapham Jct to Stratford 4tph.
• Gospel Oak to Barking halved in frequency to 2tph.
• Liverpool St to Chingford halved in frequency to 2tph.
• All services on the East London Line halved in frequency to 2tph.
• Bakerloo Line terminating at Queens Park so onwards services are London Overground only.
Chiltern Railways:
• Marylebone to Oxford halved in frequency to 1tph due to lack of demand to Bicester Village.
• Marylebone to Birmingham halved in frequency to 1tph calling at all stops either of the services called at.
• Marylebone to Gerrards Cross and High Wycombe services combined into a 1tph Marylebone to High Wycombe all stops service.
• All services that run solely in the Midlands are cancelled.
• All Kidderminster extensions are cut back to Birmingham Moor St.
LNER:
• All extensions to Skipton, Bradford, Harrogate, Hull, Glasgow, Inverness, Aberdeen, Stirling and Sunderland will not run.
• 1tph London to Edinburgh (Peterborough, Doncaster, York, Northallerton, Darlington, Durham, Newcastle, Alnmouth, Berwick)
• 1tph London to Leeds (Stevenage, Peterborough, Grantham, Newark, Doncaster, Wakefield)
Merseyrail: Halve frequencies to 2tph on every line (not Ellesmere Port as it already only has 2tph)
C2C: Halve the frequency of Fenchurch St to Shoeburyness services to 2tph.
Southeastern:
• Victoria to Bromley South cancelled.
• Charing Cross to Hayes cancelled.
• Cannon St to Orpington cancelled with Charing Cross to Sevenoaks services covering the missed stops.
• Bromley North shuttle reduced to 2tph.
• New service Cannon St to Dartford 2tph via the North Kent line calling at all stations.
• All Cannon St loop services cancelled with missed stops on the Sidcup Line added to the Charing Cross to Gravesend service.
• Charing Cross to Tunbridge Wells services cancelled with Hildenborough calls added to the Hastings services.
• Victoria to Dover Priory services reduced to 1tph.
• Peak extra services cancelled.
GWR:
• Paddington to Bristol services cancelled with missed stops added to the Paddington to Wales services.
• Paddington to Penzance/Plymouth service combined with Exeter to Penzance service with there being 1tph Paddington to Penzance calling at all stops that the Exeter to Penzance stopping service did.
• Paddington to Oxford service cancelled.
• Didcot to Oxford nonstop service cancelled.
• Reading to Gatwick service cancelled with missed stops added to the Reading to Redhill stopping service.
• All Cornish local service that run at 2tph are reduced to 1tph.
• All Brighton extensions are cancelled.