The Lisa Angel and Oliver Bonas sales have very classy things for cheap.
The Book People always have offers like extra discounts, free delivery, free gifts - and are cheap anyway. The Works and Book Depository are worth a look.
What sort of budget do you have in mind? What can you make?
You could do pamper packs if you have people who like that sort of thing - make up bag with nail files, face mask, nail varnish, toe separators, candle, bath stuff, chocolate, mini booze. Packed in a nice gift box you could do that for £10-12 easily. Pound shops sell branded nail varnish from Rimmel, Revlon, Max Factor, Maybelline etc.
For couples you could do a cosy night in hamper with a DVD (Amazon, Rakuten etc), fleecy throw (Wilko or Dunelm), bottle of wine, snacks stuff. £10-15 depending on how good you are at bargain hunting.
If anyone is a fan of Bake Off then the spin off books will be cheap in WH Smith at some point and Poundland do really nice baking stuff so you could get a mixing bowl, whisk, spatula, cupcake cases, sprinkle, oven glove etc - £10-12 all in
Right now you can buy two cheap skincare products (hand cream at 99p) and get a free nice Patisserie de Bain gift set from Superdrug (online or in store)
They might not have hobbies as such but they must have interests, likes/dislikes...