will the TT competition alloys fit the A4?

Sorry mate, not a direct fit as tts are 5x100 and a4s are 5x112

You can get adapters but alot of hassle, plus the offsets will be right off
 
ah well. back to the drawing board. really want a nice set of wheels but cant go beyond 17s really as I do a lot of miles and tyres are too dear.
 
I think Mk11 TT's are 5x112, I'm not sure what age TT Comp wheels would be.

18" tyres needn't cost more, 235/40 is a popular size. My dad has 205/?? 17's which cost the same as my 18's.
 
Comps are fitted to mk1 TTs James which are 5x100, but as you say, mk2 TTs are 5x112