Autoglym are as far as I am aware NOT BMW products.

They're available in most motor accessory shops in the UK (Halfords for example), not sure about elsewhere

http://www.autoglym.com

(I am in no way associated with this company, but I have used their products for many years and have had no complaints)

CLEANING STEPS

First of all, I put some old towels on the driveway to cover the whole engine bay area with an overlap of about a foot on all sides and parked the car over it so no grease/oil stains on the driveway.

Wrapped any obviously visible electrical connectors with cling film.

On a cold engine sprayed liberally with Autoglym Engine & Machine Cleaner (I chose this product because I read somewhere, can't remember where though, that it is not as harmful to the rubber hoses as some other products are)

Left engine standing with product on for about 10 minutes, then I carefully used a long handled soft bristle brush to loosen any major dirty patches, making sure that I did not appy too much force in areas were there were electrical or other connectors (which was not easy because the engine bay in the 4.8 is pretty cramped). This took about 30-45 minutes.

Rinsed with jet wash with pressure turned down to a level where it would not hurt my hand if it was about 6-9 inches away from the nozzle, but still more pressure than your average UK garden hose, and never directing too much pressure at any of the wrapped electrical connectors.

Used the wife's hairdryer at the coldest setting, fastest speed to dry off the worst of the water, unwrapped all the connectors and took the car for a 20 minute drive dry of the worst of the remaining water.

Once I got back home, I let the car stand to cool down for about an hour, then sprayed Autoglym Vinyl & Rubber Care on all plastic and rubber surfaces and wiped off with a soft cloth. (according to the Autoglym website you can acually just spray the product on and let it dry by itself)