The H&R springs I'm using were imported from the U.S. via understeer.com. They have a very slight lowering effect (something like 10/15mm I think). Cost was something like £140, taking into account carriage charges etc.
These are called "OE Sport" springs, which means they are roughly equivalent to the equipment BMW would fit if your car was factory-specced as a "Sport" model (i.e. has M-tech suspension).
Cheaper kits are available in the UK, but I really didn't want the drop of 30/40mm that they tend to offer.
For a full set of the Bilstein shocks, you're looking at about £25 per side for the rear, and approx £50 per side for the front, so about £150 +VAT from somewhere like EuroCarParts.
PM me if I can help further.
HF