Probikeshop.com sell Rockshox Reverb for about £165 delivered excluding bleed kit, HiBike.de sell them for about £180 delivered including bleed kit. Don't worry about ordering from Germany or France, they're every bit as reliable as UK sellers. Pay by credit card, as Paythief charges an extortionate exchange rate.
I am in the process of ordering another to go on my hardtail. The Reverb is a cracking bit of kit. Go for the 2013 version, not the 2014 Stealth, unless you fancy drilling the frame to route the hose.......
There are cheaper alternatives, but not by much, and Reverbs do what they promise to do.
Before ordering you'll need to know the seatpost diameter, overall length, the length of drop you require, and whether you want to mount the handlebar remote on the left or the right. As a guide, if you currently run a lot of exposed seatpost I'd go for a 420mm post. If not, then a 380 would do it, but may cost a bit more. As for drop, well, I like to get mine out of the way altogether on the susser, so a 125mm drop is better.
The remote lever mounts on top of the bar, and so is a bit vulnerable. Those of us in the know mount a right hand lever on the left hand of the bars upside down, or of course you could mount a left hand remote upside down on the right.
