Custom Spec Mac Pro's

is there anywhere in the uk i can get a custom spec 8 core mac pro?

for instance, i really want 4gig of ram at least...

and two 500 gig hd's, where would be the best place to order this from...?

My first thought would be this is barely custom. Can't you order it from the Apple store that way?

Apple will charge incredible amounts to put in these add-ons. See their website for pricing.
I would recommend doing it yourself because Apple makes it so easy. Find a place in your area that sells the parts you need or buy online. I am not sure what UK websites people use for Mac Pro upgrades.

Yeah, just buy a regular Mac Pro (with the lowest 8core specs) and then buy the stuff from 3rd parties

Buy the Pro you want and get memory and the hard drives from somewhere like dabs.com

I just bought a mac pro, i ordered it online. what i did was, buy the processor i wanted (2) 2.8Ghz quad intel's. Got the MINIMUM memory which was 2GB, got the HDD i wanted which was 1TB, id upgrade the rest later. I went for the 512mb Nvidia 8800GT graphics card, but i could have found that cheaper too. Got the wireless keyboard and mouse, cause its cheaper than buying it in the store. Got the wireless card also. I installed another 4GB of memory myself paying $200, easy install too. www.macsales.com Although you want to use two HD's you might want to use a raid configuration. I havent found a raid card aftermarket(the mac one is $700+!!!) I didnt buy it, but now i wish i did. Maybe another aftermarket one will pop up soon.