i got a set of those cheapo ones, jamex or supersprint, got them brand new from germany. its difficult to comment, i've had them on for about 3 weeks now, but i never tested them prior to lowering to see what the ride was like.
the car is dropped about 60-70mm and is right on its arse, the ride is extrememly bumpy over rough roads, i still do my 220mile drive down to manchester and its fine, just a bit harsh sometimes.
i haven't tried the pricey coilys, but went for a ride in my mates corsa with spax fully adjustables, and it feels just as harsh as his on full dampening. the handling of the car has gone up a lot, but sacrificed a far wedge of comfort.
if youre dropping the car any amount you're going to lose ride quality, but spend enough and you should kind of retain that OE feel. apparently weitecs are good on a budget, but you'll need to spend about £370 for the entry level ones, then about £400+ on koni's
ben