Thank you all... With any luck I'll be able to buy most of what you've suggested (certainly that PSU and Motherboard advice is useful, and will be followed) within the next few weeks (4 weeks till payday...)
I can get PC-6400 RAM cheaper at my local store than on the internet for some reason (not sure why) so I'll be making a small saving there, and possibly a larger saving on the GPU (although will be buying a 8400 to stick in the computer I'm nicking the 8800 out of)
HDDs are never a problem for me.. I generally keep my HD current, with only what I need on it. Cleaning it once a week is normal, and it gets wiped (down to OS + other liscensed software) about once a month to stop my HD from overcrowding itself...
Be nice having a HD 20-40 times larger than my current one though, so maybe won't need wiping at all, and cleaning so often...
Nice having a better GPU as well (sitting on a 32mb Matrox atm, which is going for £30 to someone... which is what i'm buying the 256mb 8400 for) and it'll be nice to utilize some more monitor space than usual...
Is it worth getting two GPUs at somepoint and doubling up my monitors? Will have at least two monitors, (possibly three) to use over 2 computers, of which one of them won't be in use continuously (only when I've got a friend round, or at LAN parties or whatever), so will be able to use two monitors if needed.
Also - did you know that Scan isn't the cheapest site out there for some parts? GPUs and DDR2 RAM (below PC-6400) is cheaper elsewhere, and 160GB HDD can be found for up to £5 cheaper... although the postage charges on the other sites often cancel out whatever bargains you get!
Did someone mention free postage from Scan when I hit 25+ posts? or is that just something I misread?