UK: I did get a reasonable discount, but via pulling in a personal favour. My local dealer couldn't match it - in fact, they wouldn't do any discount at all....! The BMW Performance brakes won't really add much to the 135i (good kit as standard) and the seats (well everything!) isn't out yet - although I don't think I'll be going for them. I might go for the exaust, air intake and short shift.
SA: Yes, I test drove the 135i. My (2001) RS4 is quite modified - including stiffer ARBs, so it actually handles fairly well, but the 135i is obviously a totally different car - RWD, much smaller, less power
For me, the fact it made me smile was the crucial factor!