R-Tech is custom mapping, nothing to do with Revo, and you would have to remove your Revo software before going there anyway
£50 + VAT fo stage 2, plus some will try to charge you an additional fee for 'set-up' time to set up the Revo settings. I emailed 4 local(ish) dealers when going Stage 2, 2 were happy to flas hthe map for £60 all, the other 2 wanted £120 which included logging and adjusting the Revo settings (you can do this yourself with VCDS and an SPS switch)
Very worthwhile upgrade though :)