Thanks vickster. The few places I've tried (inc one independent) don't have anything to try in the frame size that I'd need (I'm 6'4"). So I've been trying to whittle the options down as much as possible before taking the plunge. Halfords have been the most positive about ordering one in for me to try.
My place of work gave me a "latest" list of local independents and most of them turned out to have closed down.