The bottom line is that the chauffeur service is not operated by Emirates it is sub-contracted out.

A year ago a friend of mine was picked up in good time for a flight from LGW. Unfortunately, due to a major incident on the M25 (London Orbital Motorway) she was delayed by 4 hours and missed her flight and was classed as a no show. She had to pay the full price for a replacement ticket. When she tried to claim this back off from the chauffeur company she was shown the relevant T's & C's which absolved the company from liability in such a situation.

Fortunately she had good travel insurance