A valver is a mk1 clio, from J reg to N reg (there are a couple on H reg & I believe a few very late registered P reg ones - but i've never seen one)
They have a 1.8 16v engine & put out 137bhp when new. They do 60 in about 7.7 secs, top end is about 130 (or so)
The williams (or willy as it's often refered to) is also a mk1 clio it was from L reg to N reg, they had a 2.0 16v engine with 150bhp from the factory, 60 is about the same as valver as the valver will hit 60 in second gear, the williams doesn't you need to change into third.
A 'hybrid' is a 2.0 lump from a williams dropped into a valver (the engines look identical) apart from the exhaust manifold.
After 60 mph a williams will edge the valver, probably by a few car lengths.
Both cars came in 'phase1 & phase 2' formats.
Hope that helps. I'll probs get moaned at now by the williams boys claiming back 0.2 of second on times etc