Hello fellow R hill M5 owner!
For leather car, I swear by leatherique products. I've been buying it for a couple of years now and OMG, unbeatable (IMO at least). There is a 2 stage (rejuvenator and cleaner) combo that works magic on drying or fading leather. I order from the guy in Niagara falls, great guy and the stuff comes fast!
As far as carpets, I've just paid a detailing shop 3-40$ to just clean them up with a wet vac, but I just bought a wet shop vac so will be using that from now on.