It turns out that Channel4 are running a mashup competition. You have to use one of their Film4 feeds and mash it up with another source of content in some way.
First place is a cash prize of £1,500 with two runner-up prizes of £250 each. Of course, any submission you make can be used, cost-free by them in perpetuity (here are the rest of the rules).
The deadline is this Thursday, so good luck!