I bought my A2 from Smith Knight and Fay. I found that there work was perfectly OK, but not cheap. Currently I am using Bradford Audi as they are nearer - especially with the coil pack problems that I experienced and worries over un burnt fuel and the catalytic converter. They have been very good with me but the last service (38K) included new rear brakes, disks and pads, also new front mats came to over £600.
No Audi dealer is going to be cheap - look at the market position. I can believe that some dealers have shown little care to second hand A2's, this site has highlighted many failings but cannot understand why as there is always a prospective new/used car sale to a very satisfied customer.
I remember some years back in Germany when Mercedes anounced the A Class, "a Mercedes for the price of a Golf". My boss said that is all well and good but wait untill the former Golf owners get the Mercedes sized service bills, they won't be so happy then. I am thinking of using a local independant the next time. There is one in Skipton, they are former Whiterose VW people and looked after my old GTI very well.