Rim size will effect the handling, this can be helped by running good tyres like Good Year Eagle F1 Asymmetrics. Keep a close eye on your tyre pressure, I felt a big difference with sticking to the 33PSI front and back for my car.
If its budget you want change the wish bone rear bushes to Audi TT roadster ones,the front ones to LCR ones, fit the upper S3 strutt brace and
lower LCR/S3/R32 strutt brace.
Upper strutt brace £55
Lower Strutt brace £30
Wish bone front bushes £30
Wish bone rear bushes £60
ARB bushes £30
4 wheel alignment £60
Also with the above mods if your rear ARB is adjustable set it to stiffest setting