R Tech are apparently one of the best, along with Badger 5. But with remaps not only do you need to look at what maps the tuning company sells, but what you get with it. Some places on one hand give a free before and after dyno... Whereas a place I know in Doncaster that does revo maps gives you naff all... Just slaps it on and lets you drive away.
The best map you can get would include a free engine health check, a question and answer session about what you want from the map, any additional requirements (such as CEL delete etc), before and after dyno and possibly even a couple more dyno runs after the mapper plays with the parameters to get the very most from your car.
Shop around mate! Take your time and don't rush into the first (and definitely not the cheapest) one you see. A mate of mine has a 225 1.8 turbo TT, which he had mapped at APR tuning or some place near Worksop. He payed £240 for the bloke to come out in a van, remap the car, and leave without even opening the bonnet. First time my mate took it out he was horrified to find it was slower than before the map, and that as soon as it reached 5000 RPM the car just died like he'd hit a rev limiter. So he rang the bloke who remapped the car and he basically said it's your engine at fault, try changing the MAF, he did, still the same, he then said it's the TIP collapsing, he changed it for a forge silicone one, still the same, then he refused to comment further and denied ever mapping the car.
In the end he went to a Revo franchisee and had a before and after dyno. With the crap remap on the before run, it made a maximum of 179bhp... A whole 46bhp worse off over standard!!!
With a revo map professionally installed for £480 with full data logging session and everything, it made 264bhp.
Just goes to show, you get what you pay for usually!
Hope this helps
Ben