Hi,
I'd love to post a huge list but they're all OcUK competitors in that they sell things that OcUK sell.
Have you read the forum rules?
I presume you're actually buying a barebones laptop and then slotting in the RAM, HDD, CPU and optical drive? It's pretty straightforward once you decide what CPU and chassis you want.
I built one for a customer based on the OCZ gaming chassis and it was OK, but I could have got him a Dell for less. And the warranty on these laptop chassis is all over the place becasue they basically make a production run, then they're out of date when they're all sold, so you never get the same type of chassis back when you RMA it - even if it's only a month or so old.