One thing I will say is, ALL of the quick 172's run the Group N ECU/Rsport..... so don't write it off - It's an excellent vale for money mod.
You get a replacement ECU for around £250 - Which you could sell when you get rid of you car to recoup some money.
Hillpower sell them. I had one on mine and it was without doubt the best single mod on my car (I have ITG Maxogen, Ported Inlet manifold, Uprated fuel pressure regulator and a 2.5" bore cat back exhaust).
The only downside for me (and the reason I had it taken off) was that it didn't control the cruise on late 172's like mine. ....