Thanks for the advice guys. In the end I've decided to buy it from a reputable camera shop in the UK - it's only £100 more than the eBay price but I get the extra peace of mind, manufacturer guarantee in this country and I can easily sort it out if there's something wrong. Sometimes it's worth paying extra for good service and I'm supporting local business.

Hopefully the camera arrives in a good condition. So... anyone looking for a cheap Lumix G1 body? Mine will be going on ebay shortly....