Looks like a nice spec PC. Here's a couple of notes;
The mobo you've chosen supports DDR2-1066MHz, so you might as well use it. It's only a minor cost increase (for 4gig reckon on another £5 or so).
750W for the PSU isn't overkill. It's about right if you want it to last. Make sure it's a branded, 80+ certified unit (which i think the corsair you've mentioned is)
If you do audio recording think about getting a dedicated sound card.
For the CPU.....I would go quad core now. A q8200 costs around the same and while some of your software may run a little slower compared to E8400, a lot will be quicker now and most of the rest in a couple of years time.
The spinpoint 1TB drives are good reliable units. As you say, the cost per pound is very good. Might as well go with it! The only thing i'd say is that for an operatng system and programmes drive you're unlikely to need much more than a 500GB drive - and that includes the 50% rule (i.e. for best performance don't allow your drive to exceed 50% capacity)