Yes, they could transfer all components . . . Cost is £120 according to website, including the new cables that are likely to be needed on a larger size. As I say, my experience is that their bike-build skills are very good, I have had a total of 5 Thorn bikes (!!) and all have been trouble free, in contrast to bikes owned by other family members. A few years ago, I bought a Ripio that was on offer - a discontinued model, on offer at attractive price. 2 yrs later, I was doing more road and less trail riding, and had most of the components transferred over to a new Sherpa frame - I've never had to do anything to the bike apart from routine maintenance, mainly due I reckon to sound basic componentry and good building.
To me, the cost of getting SJSC to do the build was worth every penny. And I think that with a Rohloff bike, that would be even more important; proper installation, cable setup, eccentric etc of a Rohloff is quite a learning curve if you are not accustomed to them, and few bike shops have worked with them.
Good luck
Lewis
P.S. 5 bikes??
1) Raven Tour, purchased 13 yrs ago when I thought I might get into cycle camping etc. Seemed a good idea at the time. I never did as much 'heavy-duty' work as I was planning to, and I was never 100% happy with the fit - Thorn now acknowledge that many older riders, or those with more upright styles, may prefer short frames even with flat bars. Bike was sold to a guy who rode it to Vietnam.
2) Discovery tandem. My wife never really took to it, felt I rode downhill too fast!! But we had some good trips in Scotland and Finland on it. Now on permanent loan to friends.
3) Ripio - lovely bike, fitted it with a solid instead of suspension fork. But my needs changed, bike was transmogrified into
4) Sherpa, lightweight spec - components transferred by SJSC. Still got the bike, very good.
5) Audax, no 18 months old. Prefer it for the almost exclusively road riding I do now.
Lewis