I'm thinking of having my Brompton converted from 3 speed to 6 speed, and am wondering if anyone else has done that. How much did it cost? Did you do it yourself? How did it work out?

I understand this conversion is pretty expensive. I've seen kits online sold in England, but none in the United States. Can you get the kit in the US, or source the parts? And how hard is it to do? I think doing the work would be beyond my wrenching skills, but I'm wondering how hard it would be.

I got my Brompton second hand from a friend, barely used and for a great price, so I can't complain, but I would have chosen a 6 speed (and a different color). Part of me is tempted to get a whole new Brompton just the way I want it; that would be an extravagance, but a tempting one.