i swear there is a post somewhere about replacing your engine mounts and it only requires axle stands and new mounts which would of been probably half that price?!
they may of replaced your cambelt if that was rubbing as well when it dropped but if you get an independent opinion from a seperate garage that the work that was supposed to have been done wasnt then you have a case.
i had problems the AA as well and the garage they recommended "supposedly" replaced my clutch cable and all associated bits and bobs from clutch to peddle however took it to VW to be certain everything was done as it felt grainy when pushing the clutch down and it was found that the AA's recommendation had not replaced the snapped clutch link but WELDED it together. so wasnt happy plus they didnt replace all the parts they dais they had, got on the blower, had a word with the AA and the garage and after a few warning shots across their bows with getting the Fair trades involved and other associated bodies who deal with garage performance and award the Green Garage club to exceptional members, the AA refunded all £1500 which was the apparant labour and parts that i was supposed to have done, redid all the work and compensation with a years free Lvl 4 Euro breakdown for ALL the cars in the family.
they blamed the garage and have excommunicated them from their list of valued garages due to it.
you think it doesnt happen but it does, my current mechanic knows i'd break his fingers if he ever snuffed me on my vehicle...and then my girlfriend would disown him as a cousin lol (joking)