Help to double check the dealer please.

Hi.
Took the wifes 2003 Odyssey to the dealer with a lit SRS light, and also Brake Globe & Brake Master warning lights lit for two weeks but extinguished themselves two days ago.

Dealer says the SRS light is the drivers-side seatbelt pretensioner and that while the light is lit, the airbags won't deploy in an accident.
Its been on for about 6 days, but although the dealer hasn't replaced anything, we picked up the car and its not lit now.
Its booked in again for next week as they have to get a new seatbelt in for some Au$340 + fitting.

At the same time, we told them about the two brake warning lights that have been on but I had checked the globes and the fluid levels and they are all okay.
They mysteriously fixed themselves two days ago - just before the dealer visit.
The dealer says this is the switch inside the brake master cylinder and he wants to replace this also at $280 + fitting.

Does this all sound feasable?
Has anyone else experienced the same problem(s)?
Is the switch in the Brake M/C replaceable rather than an entire new M/C?

A reason to ask is that I have an older BMW. It also kept giving me brake globe warning lights, low coolant and some german message about the diff reselt. I checked on the BMW forum and all faults could be traced to the CCM (Common Control Module) which only needed to be unplugged and some of the circuitboard connections resoldered (dry joints) and everything was fixed.

Thanks in advance for any helpful advice.
Kind regards,