I would expect £500 at our local dealer. Not test ridden anything there in the past 2 years though so it might have changed. When I tried the 749S I took it away for most of a day to see if I could live with it. A quick ride down the road is not representative of how your back is going feel sat on a superbike for a few hours. as it happens I was hooked and bought it.
The year before that I went to Leeds to test ride an ST4s demonstrator. I signed for £500 excess there too. ON the way back I stopped at (I think) Motor Cycle City that was just up the road. I test rode the RSV Mille R there, and just before I went out the door I signed for £2500 excess. Needless to say I was nervous as hell, and didn't get the full benfit of the experience.
When the shop in Eye nr Peterborough was Carnell (or might have been Riossi by then) we went to look with some friends. I was outraged that their policy was NO test rides on anything. I asked how they expected people to part with their money for something they didn't even know they would like and the sale guy shrugged and said "people do". Good attitude (his, not mine).