Prices seem to vary quite a lot, depending on your location. My last B service at Arnold Clark in Inverness was £320, but a lot of people, on different threads, suggest a B service should cost closer to twice that.
Adding up what my first 2 services cost(an A (£230)and a B(£400)), from the records, were £630. The car was an MBUK owned car from new, and was serviced in Northern Ireland.
So looking at what mine cost from new, the £1000 doesn't look to be very good value.
Speak to the dealer about it, they may be able to advise you better on which option to take.