Try Alliance & Leicester. Usually they offer the best rates & dealers don't bother even trying to compete.
They used to offer 5.9%, but due to the credit crunch it has gone up to about 6.7%. In the current market you probably won't beat that.
If you buy a bike or car magazine, they often have a flyer advertising the latest rate in them. I think they advertise in the back of mags like Bike, etc, too.
good luck
