This is a crazy price for a fantastic camera, I imagine because it's about to be replaced by the GH2. Nearest price for body only I can find is £449.99 at Park Cameras.
The camera is great as standard. However, if you get lucky and get a pre-June 2010 model, you can "hack" this with modified firmware to get HD video bitrates of 40mbps+. The quality needs to be seen to be believed - many feel it matches and possibly surpasses the £1600+ Canon 5D MKII for HD video. If HD video is high up on your list, the hacked GH1 also beats the Canon 7D or 550D. Please research before you flame me for that comment! I know there will be lots of Canon lovers on here...
I received a hackable GH1 on the 10th October from Currys.co.uk, so there are still lots out there in the wild. It might be worth a phonecall to Harrison, they should be able to tell you what they have. Like I said though, this is still a fantastic price for a standard GH1, hackable or not.
EDIT: They also have the GH1 + 14-140mm kit lens in at £739 which, again, is a great price.