I took a look at buying the M-Performance exhaust from Cotswold BMW in the UK. They're regularly helping UK based folks (
here is a thread they run on parts pricing) ... and I used them to get a genuine M-Performance rear diffuser for my car ... landed cost was about $900 compared to $2,400 buying locally.
At the time, I recall it was going to cost about $3k landed (they had a sale going) ... so you'd have to cough for GST, but even then, it was less than half the price of buying here.
I didn't end up pulling the trigger and I'm happy with the stock exhaust ... so just sharing my experience.
Cheers,