Unless you go with some cases from SuperMicro that happen to be a few hundred dollars, pretty much every case that comes with a power supply is going to be using a very cheap and crummy power supply. While Antec is the sole exception, I think you'll find that a 350W power supply by pretty much any company out there is simply not going to be enough to power what you've got.
The CoolerMaster Stacker is a pretty sweet unit as well as Antec's P180. Same with ThermalTake's Tsunami cases. Those brand (well save ThermalTakes fugly Xaser line) have some nice, stylish cases. Not the cheapest ($100-$150 online here in the US), but some well constructed ones.
As for power supplies, a lot of UK folks have found the 480W unit from Tagan to be a helluva unit for a reasonable price. Hiper's 480W and 500W+ units would also be resonable. I've been very happy with my Enermax EG565P-VE, and you should be able to find a UK variant (I believe it to be the EG565P-AX) that would also be a good unit without having to sell a kidney.