Wow, 690 british pound? thats about $1300, which will buy you a good bit more than what you've got lined up there it would seem.
GPU: First of all, I'd dump the 6200, and go with somthing better. Honestly, you won't be happy. You'll want at least a 6600GT, but what I'd reccomend is a x800xl, you cant go wrong with 16 pipelines, and its only $270 over at newegg (all my links will be at the bottom)
RAM: Umm, make sure if you're getting 1G get 2x512 so you can do dual channel, also what kind of Corsair? ValueSelect? I run a gig of it in one of my boxes, so I like it fine, but I would still request (if possible) TwinMOS Speed Premium DDR400 (the Winbond UTT ones) instead, you can run the hell out of them and they're great paired with the AMD 64.
MoBo: I'd go with a Chaintech over that Asus, generally my prefrence, but if you don't need firewire, which it sounds like you don't, and you want a great board (my friend has this exact board with a 3000+ at 3700 speeds), this is the one
PSU: You'll need a 24pin PSU, and I don't know specifically any offhand, but anything under about 450 should do you, just please do not buy a no-name PSU or use the one that comes with your case.
CPU: I love the 3200+, but make sure you get one of the VENICE cores, you will be much, much happier.
HDD: Relly its up to you, if you have a lot of media, music etc the 120 will do you good, but 80 should be enough for normal use.
Basically this is what I'd do if I were you:
TwinMOS DDR400 41.4034 GBP ($78)
Rosewill x800xl 143.317 GBP ($270)
or if you don't wannt spring for that:
Chaintech 6600GT 89.7075 GBP (169)
vENICE CORE 3200+ 108.817 GBP (205)
Chaintech VNF4/Ultra mobo 49.3657 GBP (93)
WD Caviar 80gb 8mb cache (nothing wrong with yours, but this is cheapest) 30.2577 GBP (57)
That entire setup (with the x800) is
375 GBP, not including the dvd rw, case, or psu which will not cost you nearly 690 total, so either tariffs over there are heinous, or you could build a computer for much cheaper, one that you would then know inside and out. Or, get your freind to use those parts or somthing
sounds like you'll have a nice computer soon, nomatter what you choose to do
*edit* Also, if you're employing him, make sure you get a legal, good copy of windows xp. and I'd suggest giving him your list (which may be just what he wrote, or some of your own research, or the above or whatever) So that you know the price, (figure on shipping, tax) and agree on a rate for his services. )