My shiny new PI springs arrived last night. Gonna fit them at the weekend, keeping it on the 14" steels as I had it on 15x6.5 alloys for a few days but didn't like it at all although it did look very nice.
If you aren't fussed about going too low then 35 springs will do the job however I havnt even got mime fitted yet and I'm considering going even lower haha
Only thing is 35 springs are easy and 100 quid. Any lower and it will prob cost you a bit more and you'll need a panhard rod so you just have to decide what it is you're after.
On 15's I think you can go to about 40-50mm drop without any problems