Office Christmas meals *shudder*
To lessen the blow, try one of these lovely establishments who have usefully indicated which of their menu items are gluten free. Meaning, you can get on with avoiding the office sleaze-bag and curtailing your drinking around the 'big boss' rather than painfully explaining to the waiter/waitress why you can't eat flour.
http://www.iguanas.co.uk/pdf_menus/las-iguanas-christmas-menu-2011-ROW.pdf (Not exactly my taste and the last meal I had here was clearly microwaved and saltier than the dead sea but nevertheless it's easy, reasonably priced and they have cocktails.)
http://www.brasserieblanc.com/christmas/26.php (Ooh posh. I like Raymond and I would like to eat here so I can picture him barking demands at his staff, like "get zees sheet out of 'ere!")
http://www.glassboat.co.uk/wp-content/uploads/2011/07/xmas_2011.pdf (My husband and I ate here a while back. The atmosphere is lovely, the staff attentive and the food pretty good. Worth the prices for the view of the river and superb wine pairings.)
I'm afraid that's all I could find (and I looked at a lot!) Will update if I find any more.