Obvious choice for Kensington would be looking in to Chelsea tickets, given the proximity, but they're difficult to get hold of as their stadium is small, so they tend to sell out and not go on general sale.
I'd recommend them looking at a Tottenham home game, as they're currently playing at Wembley whilst their own stadium is being built. They haven't sold out any games there, as it's much bigger than their home ground, so their tickets have been going on general sale.
A quick check says they're playing home games on the 15th, 26th and 29th December.
This link should be useful. Also gives a list of ticket sellers to avoid, which is cool:https://i.tottenhamhotspur.com/hc/en-us ... nformation