Hi,
Standard price across all revo agents 499 + Vat = £586, the thing with revo is that even if the agent had a rr the map cannot be tuned to your car as it is a generic remap (although it can but switched to different preferences with sps switches, would have been good to get the figures before and after but the difference is amazing. Car is just a year old so did not have any probs anyway, i believe that they did check with vag.com for fault codes before and after anyway.
If you are wanting rr custom re-map your best bet is either Jim at Star who now does his own maps or possibbly Bedrock Veedubs in Motherwell who are the Jabba agents both of which have rr's, it a personal choice, I would have gone for Jabba but as I said they did not have the map for my car, they should have one for the S3's though but I believe they change the actual chip.
Best of luck whatever you decide but certainley worth doing which ever route you decide on.