Had 2 new rear tyres on the Z4 (07 2.0i Sport) yesterday and whilst the wheels were off had a look at the brake pads and also the rear springs. The o/s spring was broken, about 2 coils from the bottom - similar to Gaz :head:
Tried RealOEM but it doesn't recognise the VIN number as the 2.0i Sport was a separate model so couldn't get a part number therefore no choice but to contact the local dealer - Sandal BMW in Wakefield. Phoned them about 3pm and rear springs are special order parts at £99 (incl VAT) each fortunately they were quite happy to sell just one! They phoned just after 9am this morning to say that it had arrived so off to collect it.
Couldn't find anything on Youtube for the E85 but did find
This One for an E46. Followed this and used the jack from the Z3 and it was quite straightforward - took about an hour taking it slowly and carefully.
The Part Number for the o/s rear spring is: B33.53.6.761.924 and it was marked with 3 Silver marks for the lowered suspension option.