Hi there danny,
The best Springs would probably be the EIBACH .
As recommended by most here (or they did when I asked a similar Q)
Excellent quality and really makes a difference to the stance of your
Ibiza.....
However, if you have the cash, you really are better off with a full set of Coilovers (Kit). Fully adjustable, also you'd be able to drop the car even lower! But you would be looking around £450+ .