check out gumtree and netmums childcare boards. lots of student teachers and student nurses will be off in december so may be able to get one of them for 2wks i know many do look for holiday childcare work.
I am close to you, I may be able to help and could give you numbers for good agencies in our area. Please let me know on here if you contact me as emails sometimes go straight to bin! surreynannny at hotmail dot co dot uk