Hi Guys,
Thanks for your comments so far. I have specialist springs, shocks, Panhard roll bar etc all designed expecially for this drop on order, and to be fair it doesn't sit as low as it sounds (see pic of one with same set up below). I'm also probably going to run 16" wheels now which will also give me a little clearence back.
I've spoke to a few guys running the same set up and they're very happy with it and everything can be returned to stock if required.
Still confused about the wheel offsets/backspace i should be looking at however.
Oh and this is my car: