Great Western Coffee Shop

I hope to travel from London to the west on the 18-03 on the thursday preceeding Christmas.
Is it likely to be unusually busy due to the holidays ? or will most have already left London ?

I would propose to book a seat in the Pullman, so in theory is does not matter how busy the rest of the train is, but in practice I dont want to fight for my seat, or find that first has been declassified.

Any advice ?

It's highly unlikely 1st Class will be declassified unless there is some serious disruption. I'd imagine the 1803 to be it's usual busy self, perhaps a little more so on the 20th, so booking a seat in the Pullman would be advisable.

Who knows, FGW might even provide a festive twist to their Pullman offering. A few years ago on the Pullman in the run up to Christmas I had some mulled wine and was offered a mince pie. I declined the latter - horrible things.

With Christmas falling as it does this year I would think Friday 21st will be vey busy whilst 24th might be quite quite.

I would expect 20th to be more busy than a normal Thursday as people follow your lead and get away early to miss the Friday rush.

I have just purchased my ticket and was suprised at the low price.
The availability of such discounted tickets may suggest that the train is not expected to be busy, which would be suprising.