Does anybody have an idea of servicing costs of BSA , AA and DS compared to the independents?

I've always used John Bowkett but have an AA 400, a Falcon and a S10 to service. May be worth sending to an independent to do a one stop shop but as I'll be selling them I'd prefer a factory service as they have not been used by me for a long time and have come back off loan.

thanks in advance

Gary