My DS is vegan and I am collecting stuff for a hamper/food package for him at Xmas that will go back to university with him to keep him supplied with treats in January.
Hotel chocolat/montezumas staff are great and will point you to dark chocolates in their range which are vegan. You can also easily identify dark bars in m and s, green and blacks etc if you want to spend less. Some after eight style chocolates, though not actual after eights, are vegan. DS also likes dairy free chocolates from moo free which you can buy in holland and Barrett and from ocado as they are more milk chocolate style - packaging suggests they are aimed at children. I also get him a heap of naked bars.
Cheap biscuit wise most bourbons and Aldi dark chocolate digestives are vegan. Going up market lots of free from stuff will be vegan, but need to check everything (honey and egg are obviously often in dairy free stuff).
I buy him nice nuts - cashews, almonds etc. Nice cordial is obviously vegan. There are lots of websites to check for what alcohol is ok so easy to get wine, beer, champagne which is fine.
I've ordered vegan chocolate spread from ocado as his siblings have personalised Nutella from Selfridges. Ocado is actually a pretty good source of stuff if you just search on vegan. Most is normal groceries, but obviously treat stuff does come up too.
Posh jam is almost invariably vegan!
Many deluxe hot chocolate powders are vegan.
Some supermarket mince pies are vegan, obviously have to avoid posh ones with butter in the pastry but from memory I think Asda standard ones are ok. It's easy to make a vegan CHRISTMAS cake.
If you want to include toiletries most lush stuff is vegan, but check as they have honey etc in some stuff. Down market coop and Superdrug own brands are also vegan friendly, not sure why the distinction from other brands, but DS definitely makes it.