Here's my views on First class travel:
Best lounge: Great Western
They might only have two, but without a doubt they offer the best service. I can't speak too much for the Cardiff lounge as I've only been in there maybe 2 or 3 times in the last 10 years, but the lounge at Paddington is excellent; offering sandwiches at lunchtime and delicious cakes throughout the afternoon. There is also complimentary wine and cocktails at certain times.
Best (inclusive) breakfast: East Midlands
There are a handful of trains in the morning that offer a "Full Breakfast." Freshly cooked onboard the train I would say it is the biggest and best breakfast, with the exception of Pullman on Great Western.
Best lunch: East Coast
I know it gets a bit of criticism, but I quite like East Coast's All Day Menu. It rotates often enough and always has something on there that I like, and in more recent times they are a lot less "stingy" with the portion sizes, in my opinion. Complimentary alcohol, including spirits, is also available.
Best dinner: Trains Wales "Wag Express"
Three course meal, very filling, and very attentive service.
If there had to be a second place because of the limited service, then I would award it to East Coast, for either the All Day Menu or Evening Meal Menu, as I think both are perfectly acceptable.
Best weekend service: East Coast
The only Toc that gives you something decent to eat on a weekend. It might only be sandwiches, but it's better than what other Tocs give you.
Best staff: Hull Trains
I've only done the (Love) Hull Trains First class on a weekdays and had an enjoyable lamb hotpot on both occasions, served with warm bread roll. Food was microwaved but very high quality so this was not an issue. Onboard ambience was good for a DMU, but the seats didn't align with the windows very well. Having a dedicated First class host for only one coach meant that it was always easy to get a top-up, or anything else that I wanted.
Nicest ambience: Great Western
I really enjoy travelling on the Great Western refurbished HSTs. Nice, luxurious and comfortable seats, and also a good amount of privacy.
Not as bad as everyone says: CrossCountry
The offer onboard CrossCountry is much improved compared to Virgin days, with the availability of the First class host extended, and also the quantity and quality of onboard offer much better. However it's by no means the best, and also the limited operating hours (no catering at all after 8pm on most routes) means I can't rate them too highly.
Best hot drinks: Hull Trains
Before departure, a large mug and saucer with biscuit, and a milk jug is placed on your table. The host leaves you a few teabags (Yorkshire Gold) and is often popping back and forth offering refills.
Best cold/ambient drinks: Tie between East Coast and West Coast
I think the offer during the week is pretty much the same, they all include apple juice and orange juice, coke, spirits and wines.
Overall best: East Coast
All round, taking in their lounges (especially now they have been refurbished), and the offer available throughout the week, including weekends, I think East Coast offer the best service. The breakfast isn't bad, and drinks are usually served in china cups/glasses rather than disposables. They offer an excellent lunchtime menu and are the only ones to offer you anything decent on a weekend.
Overhyped: West Coast
I enjoy travelling West Coast, and I think their breakfast is decent, but overall I don't think they are as great as everyone makes out. The Euston lounge in particular is very tatty and doesn't have a great ambience. They don't rotate their menu very often which means you can be eating the same stuff for months on end, and the portion sizes are also very small. Their weekend offer is terrible. There are a few gems though, I think some of their lounges are quite decent, and I would probably rate New Street's lounge as 2nd after Paddington.