Chocolate truffles? I think they are just double cream and dark chocolate, maybe a bit of rum, and then dusted in cocoa powder.
Amaretti biscuits - egg whites, icing sugar and ground almonds. This recipe also has amaretto liqueur in, but I've definitely made them without. I also make them bite-size rather than as normal biscuit sizes - probably need a bit less cooking that way.
I've made both of these before (but can't remember the truffle recipe - sorry!) and they are pretty easy, tasty and look special!
On the savoury side, what about some herb vinegar or oil? No idea how to do it, but I don't think it can be too difficult and you could then put it in a decorative glass bottle.
Great idea - hope you have fun doing it!
FWIW, when I've done a hamper, we've actually found really lovely stuff in Waitrose, and at a much more reasonable price than Selfridges, so you might want to try there. They do a great range of teas, coffees, mustard, oil, fancy pasta etc.