I have been looking at them too for a £1000ish system and have emailed them over a week ago but got no response.
I also looked at pcspecialist but am now disuaded from them as they ask for debit cards or cash and cheque and refuse to take credit cards. So your choice of machine, supplier is also dependant on their service too. I have not received any reply from pentathlon and now take that as a sign not to buy from. Imagine you just spent your hard earned cash, then the computer dont work and you can get hold of anyone to come out and fix.
That is my worry, so my money is staying in my pocket and I will take my time before spending it on a worthy supplier and spec