There's a company called "Bakehouse", I believe they're Irish. I don't know where their stuff is normally available in the UK, but they sometimes turn up at our local "discount frozen food shop".
Their chocolate chip cookies are amongst the finest biscuits I've ever eaten.
Anyway, they also do a vegan range. I'm not vegan, but if you're going to sell posh packets of biscuits at 39p or less, I'm going to try them. They did some sort of chocolate/nut ones. Delicious, I thought.
Nairns also do (or did?) gluten free biscuits and oatcakes which were lovely. I think they sell these in one of the big supermarkets, but they're expensive. I wouldn't have identified them as gluten free of it didn't say so.