i feel your pain mate, i spent ages looking around. the only place i found to insure me short term was
http://www.insuredaily.co.uk/ they only cover a range of cars and im 21... they are also expensive, i was looking at £35 for a day!
I can understand theravens hostility, its f**king annoying that no one insures undr 25s properly, the fact that im a student makes my insurance worse anyway. If somone suggests to use google, when if they themselfs did, they would see that no one insures under 25s in this way, its pretty annoying.