Hard to know what 25bn will pay for, but my list is:
- Buy a profitable rail company to subsidise the railways (let's get into the European Railfreight and HSR Open Access game)
- Commit to a rolling electrification programme: Chiltern-Snow Hills & EWR, remaining Southern Region routes, easy branch lines, Leeds-Selby-Hull, Bristol-Derby, Felixstowe-Ipswich-Ely-Peterborough-Birmingham, support Scottish electrification plans...
- Complete electrification of: MML (all the way to Doncaster/Wakefield & Erewash Valley), Great Western, TransPennine.
- Reopen: Woodhead (Hope Valley isn't good enough), Leicester-Burton, Portishead, Sutton Park, Walsall-Brownhills-Lichfield
- Extend: Crossrail - Heathrow-Staines
- Major upgrades: Castfield Corridor, Woking Flyover, Newark Flat Crossing, East Croydon-Norwood Junction remodelling. And 4 tracking of: Dorridge-Moor St, Leeds Eastern Approach, Tottenham Hale-Cheshunt
- Stations Rebuild/big referbs of: Stratford, East Croydon, Norwood Junction, Elephant & Castle, and anywhere else that's pressing. New platforms for Brockley (Nunhead link), Clapham High Street (Southeastern)
- Upgrade programmes of the South London and West Midlands suburban networks - not too crazy: station referbs, higher frequencies where possible, new fleets where needed, ticket gates
- Actual unified signage, not half asked attempts
- Fleet - Lengthen more 5 car Intercity stock to 8-10 cars