Considuring the cars i'm looking at may be between 6 months and 18 months old, i'm sure it would invalidate the warranty. Tho i'm considuring using this car for some significant amount of time. I could quite happily get used to a 150bhp car with no mods from my current 62bhp 1.4i astra and slowly mod it when the warranty ran out.
I'm sure it would be more sensible to add mods over time, when A) my insurance is going to be cheaper, when i turn 25 in a years time and B) i'm use to running with 150bhp.
I don't want to wreck my car, as i'd have to get used to 4 wheel drive as well, and i'm sure that definitely is a noticable difference, (Total traction? - i hope)
TiG