Dafydd, I've been on two Arvon courses and would highly rate the experience generally.
Dee's right that there's some mucking in, but it's a bit like staying in a big family home with a load of people who very quickly seem like friends - nothing like going on a businessy course in a hotel!
As for cooking, Dee, you cook in a team, so if you said you were veggie and wouldn't touch meat I'm sure they'd let you just chop veggies etc and not go near the meat - though you might have to be in the same room as it. But then, if you eat in any restaurant that isn't totally veggie you're in the same room as others eating meat, and your food has been cooked in the same kitchen as meat is cooked.
I have difficult dietary requirements (coeliac etc) and on both occasions the staff and other students were lovely about helping me with them. Being veggie will be something they're very used to!
I found that the biggest benefit of such a course was meeting other would-be writers and the tutors, who are very accessible, since you eat with them and spend time with them. Usually you will workshop some of your writing (co-crit with everyone) and usually there are also seminars where you all work on particular skills. And individual sessions with the tutors. There's a lot of time for writing alone too, and going for long walks in lovely countryside to get inspired, and the drinking.... well, there's lots of sitting around in the evening talking into the small hours, with or without wine as per your preference!
I would say that I felt I gained more in terms of how writers think and feel and work than I did in actual hard specific learning, but the former was just as valuable if not more so, since you can get the latter from a book to some extent. And you can get both from WW!
And of course you can pick the course which seems to most closely match where you feel you are or the genre you're interested in... lots of choice.
I hope you give it a try, since I think there's a 95% chance you'll really love it!
Deb