Referring to the view that Thorn tend to sell bikes too small, that has not been my experience. So far with me, their sizing has been spot on - though I am pleased to see that the latest brochures advise that many quite a few women, and some older men adopting an upright position, will get on better with an S frame on straight bars - I come into that category!!
I recently bought a new Sherpa frame /forks, and swapped all the components from my Ripio onto it. I will be writing up about that before long. I submitted my measurements, set up of existing bike etc., and Steve at Thorn recommended a 530S. I was uncertain, thinking a 500S might suit me better. They put both frames aside pending a fitting session, at which Steve confirmed his view that the 530S was for me. I agreed with him.
And the bike has proved to be a superb fit, very comfortable.
The lightweight spec Sherpa has turned out to be a brilliant bike, more about that later.
Lewis