My sister has coeliac disease and we recently flew Club to New York. On the outbound the gluten-free food was very uninspired: Rubbery solid bread rolls (inedible), a large chunk of white fish and some boiled potato. No colour or flavour at all. The crew were ashamed to serve it. Coeliacs are not all health nuts and do enjoy spice and variety. In the end she and the crew had a laugh about the abominable food.
The food was better on the way back from JFK but it was no laughing matter as the sauce she was served with her dish was not gluten-free (she later discovered) and she spent a large part of the flight and the next day in agony. She was offered no breakfast (besides a normal croissant by a passing crew member). To top this all off she went to the loo and the door fell off and landed on her, trapping her in the loo until she could get a crew member's attention. Needless to say she wrote 3 times to BA before she got a response; an apology but no offer of any compensation. She does wonder why I love BA so much.
Be prepared for a dull experience and take your own sauces with you if you can. Don't count on the crew being trained regarding gluten-free items on the menu. Awareness of this issue is low in general, and most people seem to think gluten-free requests are a faddy diet choice, rather than a health necessity.