Evans will let you demo a bike and refund the £50 if you just turn up! But I think their demo is limited to the car park.
My LBS charges £50 as well, but you get as many bikes as you want for 24 hours at a time within 30 days and occasionaly does demo days where they get a few importers to bring their demo fleet over.
Anohter option if you’re part of a club is to go directly to the distributor, we’ve had Orange bring their fleet down for a mid week night ride, although the guy looked less than happy when (another STWer) someone launched the demo 5 off the big drop on Stripes in Guisbrough, the bottom out was a little ‘harsh’!