I don't know how the situation in the UK differs from here, but I've found the best real bargains with buying from the web, from established makers.

Nearly everyone I know who's shopped for a "bargain" machine has come up with a decent machine; but the software bundled with it has been disappointing, and upgrading the software would cost about as much as the original price they paid (and more than they "saved.")

I haven't found a machine for my last 2 or 3 purchases that came with a really good sound system, although none of them have been in the "terrible" category; but I had to add on a sound unit to my current (newest) main machine because it came without a midi jack - replaced by seven surround-sound speaker jacks on the backplate.

It's always the little things that get 'ya.

John