If you read that bit above again, it states "Please note all vehicle repairs and warranty claims must be completed by an Approved BMW Dealership....." rather than all servicing, vehicle repairs etc.
You can have the car serviced anywhere, provided you use OEM parts. For the sake of a few quid and the potential hassle of proving what you had done, with which bits and by whom, just let BMW service it. That's what I do and I've never had an issue with any Mondial warranty claim. Think I had about £2.5k's worth of work done on the M3 last year.