other than just by checking on the packaging im not sure. i think a lot will say suitable for vegans these days. Tesco have their 'Free From' range which are gluten free and generally suitable for Vegans. Otherwise go to www.goodnessdirect.co.uk which sell vegan products delivered to your door
apparently Tescos bourbon biscuits are suitable for Vegans - not sure if this is correct or not...you'll have to have a look at the ingredients but at least it saves you checking the labels on the whole shelf!