Travel to London for two days

Friends,

I am an Indian living in Sao Paulo Brasil. I would be visiting London for two days and then travel to India; just to catch up Christmas in London. I would like to know is there any place where the accommodation is not expensive and anybody has a plan to spend Christmas somewhere. I might be there on 24 th and 25th Dec.

Also, I might need a transit visa. Do you have any info on that?