Bought a 164 off ***** & yapps this summer. Wasn't entirely impressed that despite having a full service, the radiator fan fuse was missing, causing it to over heat.
The heater fan control also failed, which they did admittedly fix, but not the control illumination bulb, and at the same time left a large screwdriver under the drivers seat ( ound when it rolled under the pedals as I braked to give way to a bus- took screwdriver back, got no apology)
Additionally, at the last service they recommended that I change the rear brake discs. Their quote was £325 for parts+ 2 hrs labour.
Talked to another specialist, they quoted £130 parts+ 2 hrs labour. Small difference.
I shall continue to deal with them while the warrantee lasts, but unless they improve, not after.
LC motors (http://www.lcmotors.co.uk/
)got good reports on the GTVV6 site.
If you don't mind coming over the bridge, Automeo is good (http://www.automeo.co.uk/
Hope that helps.
If you've already tried A&Y's, it'd be interesting to see what you think.