MSN news from Trainline tells us that the quietest days to travel are Christmas Eve (24th December) and Sunday 22nd December. Busiest day of the lot expected to be Saturday 21st December, with Monday 23rd December second busiest.
They tell us that no trains will operate on 25th December and only some very limited airport services on 26th ... that latter contrary to Real Time Trains which, for example, has a London Marylebone to Oxford Parkway service showing, a whole lot of services on Merseyrail, and if you're in Glasgow you can get to Ayr, Gourock, Motherwell, Larkhall, Neilston, Kilmarnock, ... even to Edinburgh and with a change of trains to Leven!
* From 27th to 29th, Paddington closed (so really from 25th to 29th)
* Liverpool Street closed from 25th December to 2nd January
* Crewe closed from 27th December to 3rd January (so really from 25th to 3rd January)
* St Pancras to Harpenden closed 21st to 29th December (East Midlands trains starting north from Bedford
The article does not cover the closure of Westbury from 24th December to 24th January 2025 - that's 30 days. Perhaps that's because they regard it as a long term closure rather than a Christmas Story? But with trains timetabled when open from Westbury on 6 lines - to Cardiff, to Portsmouth, to Weymouth, to London, to Swindon and to and via Taunton to the West Country, the shutting of "the west's Crewe" for a month deserves a mention, surely!