Nice one andlid, thanks for the advice.
If I'm going to buy the new wheels soon then I will go gentle and live with the issue I currently have. I don't want to spend £500 on new tyres for the 17" wheels then go and buy the 5Zigen's and have to buy tyres for them as well, that'll eat in to me sweet fund far too much!
I had considered the Bridgestone RE050 A's, Falken 452's and the Michellin Pilot Sport 3's, but I was a bit concerned about how soft the sidewall was on the PS 3's. Hadn't thought about the Goodyear F1's though, so I shall check them out as well.
Sounds like the tyres I have on my 17's at the rear certainly aren't right. So if if it is going to be a while before I do get the new 19" wheels I will consider replacing the current rears with 235/50/17, which is cool