That all sounds good
As for UK sites, I love this:
I'm from the UK too, and tend to use this shop for PC upgrade buying, as they are competitive with pricing, which makes them cheap.
Its also very coopretive, and you get your products at the times you suggest. I couldn't rate it any higher than I do already.
The only issue I can see though, is the fact the motherboard you requested isn't listed...
It has one PCI-E and AGP board in stock, but theres no SLI support, or Dual Core support.
I believe this site has that motherboard though, from a google search:
They seem cosure, but I haven't used them.
You'll need to sign up though, which is free before you can start selecting to buy.
After you've got that board from them, I suggest Microdirect as your next port of call for the other parts, unless you can find them for the same price on that site.
Take your pick from no other than Micro Direct
It depends on your case colour, etc, though the 16x ones are definietly fast enough to play DVD's, etc.
If you want a burner for later, you'll have to pay a bit extra, though £10 more won't break the bank for DVD/CD burn support at 16x DVD+R, and 48x CD-R compared to a standard DVD/CD reader only.
Your choice, but I think that'd be a good bargain, and thats a really good DVD burn speed too. I only have a slow 4x DVD burner and it cost more than that
I hope this helps