I would opt for the Antec 1200 & Antec 850W bundle click here instead for only £6-7 extra. The 1200 is larger though, but should be easier to work with. The Antec 850W PSU with 4x dedicated PCI-E connectors has a distinct advantage over the 2-connector Be Quiet 650W.
Consider at least 3 other HD4890s that may have better coolers for similar money, e.g. MSI click here, HIS click here & Asus click here. Asus GPUs (& motherboards) carry a 3-year warranty click here.
Yes, you'll be fine without the aftermarket cooler, which is really only necessary if you're going to overclock the CPU.
Save £20 by getting Win7 for £65 from Amazon click here or Dixons click here.
You may want to reconsider going for a XtremeGamer 7.1 card & 2.1 speakers - you'll get next to no benefit compared to the onboard motherboard audio. And at £70+, I reckon it's grossly over-priced - it used to sell for £30 less a few months ago. G