firstly, welcome!
secondly, have a look in the Forced Induction area of the forum. lots of info in there, then go to my350z.com for just about anything you want answered has already been asked over there.
main thing you need to know - your stock engine can go up to 400bhp, anything more and you will need a built engine (new forged internals)
Local installers - not really. Although RSTuning in Leeds may do it. Mines going to Abbey Motorsport nr the M25! Although if you ask nicely, Falcon Performance in boro may give it a shot.
Best type - depends. Do some research on here and my350z. lots of reviews.
bodykits etc - www.z-store.co.uk is mail order, and in the North East. And Falcon Performance in boro could do spraying and fitting.
Al