Not sure about all of the kit, in fact I'm not sure exactly what it consists of on the W212 any more, but there are a few pieces available from Kunzmann. They are good to deal with and ship regularly to the UK but, and quite a big but, it may not be the cheapest option doing it this way.
There's an example
HERE of the diffuser and tailpipes, it may be worth a browse round their site whilst you're looking...