I can understand your frustration and agree it's a pain to have to do so much leg work to get the best price. I also agree with the above in that's it's not a customer service issue is it? Did they treat you badly, with lack of respect, didn't care?
Ultimately they are franchises and can charge want they like. As with all dealers, it is luck as to whether the one closest to you is good. I have found Woodford to be very good and Toyota in chelmsford. Very polite, always get courtesy calls pre and post service, offered tea and biscuit on arrival etc.
Sorry you are thinking of selling.
Stu