There's a Christmas market on today in Christ Church Cathedral today from 11 am to 4 pm. It'll be on again next Saturday (10th) and the one after that (17th). I went along last week to take a look - the market is in the crypt of the cathedral, which is pretty interesting in its own right. There are about 15 stalls featuring a range of arts, crafts, jewellery and a few seasonally-themed goods. The venue has a lovely, warm atmosphere.
There are also several food stalls outside in the open air.
As an aside, I was delighted to see a display in the crypts showing costumes from the TV series The Tudors. Parts of the series were shot in Christ Church, and I had the interesting experience of being an Extra for the day.