My car was parked up for a few weeks whilst I was away. On starting for the first time (and continuing), the airbag warning light remains permanently on. I've checked under the seats to see if there is an undone cable but all seems OK.

My local garage doesn't have the diagnostic equipment and suggest going to a franchised dealer for this. If you have any suggestions as to the cause, it would be appreciated. If I have to go to the franchised dealer (whom I have used in the past and have a poor reputation) how do I avoid getting ripped off if they suggest an new ECU etc?