The Panasonic Lumix G1 with the 14-45mm lens kit is just £329 delivered with Jessops at the moment with the £50 cashback available until 18th July. 4% Quidco available as well which makes it even cheaper. Could be as little as around £314 depending upon how the cashback is calculated.
This is the cheapest that I have seen this yet, though Currys were supposed to have a few knocking around in store for slightly less, if you can find one. Nothing in my area as usual with these Curry's deals.