www.met.police.uk/christmastree
Such a simple idea, and a lovely thing to do if you can. Basically, you sign up with your area (London this is, but I believe other areas do similar) and say how many gifts you want to buy. They then assign you a child who may not otherwise receive presents (or children if you’ve picked more than 1) and give you their gender and age. You then buy an appropriate gift and drop it at any police station, unwrapped (gift bag is fine) with the unique reference number you get on it. I’ve done it a few years running now.