Silly comments!?
There are people on here who know what there on about too Tom.......Some if not most have had the 1.8 and 2.0 engines prior to 172s/182's so will know about tuning. If you want to be told what you want to here rather than the truth by all means trot over to williamsclio!!!
The lads and lasses over on WC have a damn site better knowledge on the F7 series engines than people on here full stop, I'd have thought that was pretty obvious as ALL the fastest Mk1 Clio are on there... in fact all the fastest 2.0 N/A Clio's are on there. Fact, not fiction.
Companies with the best results have been:
AWT with Martin's car, that ran a 13.4 @ 103 iirc when Mehdi had it. Full ITB setup with cams, stand alone management etc etc
Hill Power with Martin's old hybrid, that ran a 13.8 SQM. Was stripped to the balls, but still a very impressive time none the less.
GDI - the infamous Nana ran a 14.1 on standard rev limit, was running 185bhp in that trim, but has since had headwork and been mapped on the RR again to 7'400 iirc, so running 197bhp I think.
Other people like 2 live have done all the work themselves to their car and he was the first person to crack a 14.0 dead with only the back bench and spare wheel removed.
It's up to you, but I've only taken my Clio's to a couple of people. I've had work done by BenR @ AWT (when I had the Williams) and Andy @ GDI (for my ITB'd 17poo). Ric Wood is also very good, but prolly a bit too far from you being near Manchester.
Just to add, this following thread gives an indication of where all the quickest cars are being produced... there's a distinct pattern
http://cliosport.net/forum/showthread.php?t=195389&page=2