What actually happened.
In accordance with my general policy when travelling intercity, to catch one feeder train earlier than scheduled, we departed Southport on the 12:21 Merseyrail service to Liverpool Central.
Ignoring the journey planner instructions to change at Moorfields to the Merseyrail line to Lime Street we alighted at Liverpool Central and walked to Lime Street where we boarded the intended 1343 Avanti service for London Euston.
At about 1505 this train came to a stand at Nuneaton. By 1520 it was announced that due to an incident north of Watford further progress was unlikely any time soon. The train was soon joined at Nuneaton by another Avanti service (from Manchester). Passengers for London were advised by the Avanti train manager to travel onwards via Leicester.
We boarded the 1551 Crosscountry Service (destination Stansted Airport) for Leicester.
The online journey planner now replanned the journey with an arrival time at Billericay of 18.53 (89 minutes late).
On arrival at Leicester we transferred to the 1630 East Midland Train Service to St. Pancras. Ontime arrival at St. Pancras at 1739. Avoided the need to walk from Euston to St. Pancras. Caught first available Thameslink service (destination Horsham) to Farringdon. At Farringdon a one-way flow system was in operation preventing access to the Elizabeth Line from the Thameslink station apart from by lifts for which there were long queues of people with pushchairs, huge suitcases, children etc. We walk through the streets, including through Smithfield market to gain access at the other end of the station.
Took the second available Elizabeth line train (destination Shenfield) (first one was crush loaded) as far as Stratford. Boarded the next GA service to Southend Victoria, (due at Billericay at 1853 in accordance with replanned itinerary) which having left Liverpool Street on time was delayed at Stratford by a freight train passing towards the North London line, and arrived at Billericay 1859.
Return journey:
Again in line with policy of catching feeder train one earlier than scheduled, departed Billericay at 1437 for Stratford on GA service to Liverpool Street. This train was terminated at Shenfield due to a track fault at Ilford. It was soon joined by a service from Ipswich, which the ex-Southend train passengers, including us, boarded. This train was also terminated. Station announcer recommended passengers transfer to the Elizabeth Line, so we boarded the 1503 service from platform 6. As we departed we saw what we presumed to be the 1457 (ex-Billericay) GA service pass us on the fast line. (Real Time Trains confirms this train ran on time arriving Stratford at 1524). The Elizabeth Line train lost time, passed Stratford at 1542, reached Farringdon at 1554. The one-way system at Farringdon was not in operation, but would have been in our favour. Boarded next Thameslink train (9R52 destination Bedford) arrived St. Pancras 1605. (This was only 5 minutes behind my planned itinerary, had we been on the 1457 from Billericay). Walked to Euston, and arrived at platform 12 10 minutes prior to the departure of the booked 1630 departure to Wigan NW. This service ran on time. From Wigan Wallgate, took the delayed 1852 Northern service to Southport arriving at 1930.
That is the real world.