If you want to choose ALL repeat ALL components, use the configurator.
If you want to choose only SOME of the components, including the CPU, you need to find a "barebones" that has no CPU, but will accept a Phenom.
It seems that most UK providers do not do "barebones" of any type.
The barebones offers vary from time to time. If a supplier does not have a Phenom-compliant barebones kit this month, they may have one next month.
The only advantage of barebones is possibly on price.
I'd keep looking at OverclockersUK, or call them, or try to find another barebones supplier, or don't bother with barebones.