Lempure,
Rohloff have a dealer finder here:
http://www.rohloff.de/en/service/dealer_finder/index.htmlI'm not sure where your bike is in Limousin, but using Limoges as the search city, there are 7 Rohloff dealers within 200km including Brive-la-Gaillarde to the south and one just east of Gueret.
I believe I would pursue a dealer from this list, as they will already be familiar with the Rohloff hub and may even be local to your cottage.
If the listed Rohloff dealers are too far from you, then perhaps this similar query regarding ateliers velo (bicycle workshops) and dealers in Limousin will prove helpful to you; there are some reviews, though not much in depth:
http://www.completefrance.com/cs/forums/731442/ShowPost.aspxThe French Yellow Pages (
www.pagesjaunes.fr ) list a number of shops in Limoges, but no user reviews or quality assessments, unfortunately, and it would be a shame to have someone make a hash job of it.
I suppose you could always send the wheels to Thorn, but the shipping charges could add considerably to the cost, and there might also be duties to be paid.
I think the change to lighter rims and tires will make a marked difference in the feel of your RT. I know forum member jags is considering a similar approach to make his Sherpa more lively and sporty to ride when he isn't using it for loaded tours. A review of his posts might prove helpful as well.
Best,
Dan.