you can even get 20's on them lol 19's seem to be o.k
as for suspension it entirly depends on what you want to spend
i would recommend coilovers thoughover normal lowering springs
Coilovers are the ultimate but no good if you want ride quality - depends what you want from the car TBH.
What would you suggest Rich??
I could do with sorting out the roll, but i dont want a rock Ard ride. 
just change the springs, or shocks aswell??
Any ideas? 
Right first How low do you want it? Look at some pics at the top of this page.
If you only want a small (30mm) drop go with eibach pro spings or if you want that bit more eibach sport springs.
The pro springs are the best compromise between good ride and handling. Sports are a bit firmer.
Best to get matching dampers aswell IMO tho eibach say thay will work fine with your standard shocks - prob wear quicker tho.
The thing is if you dont like the ride height you have gone for you cant change it with springs - but obviously you can choose the ride height with coilovers.
HTH