Disappointing service from Nissan

[MrsSBr]

We bought a Nissan Micra from Nissan's official dealership (Bishops of Guildford, Surrey).  No checks had been done prior to it being put up for sale, the wrong mileage was recorded on the paperwork, the tyre tread was low (despite being told by the sales team that it would be a minimum 3mm, it received an advisory rating in an MOT 4 months and 4000 miles later) and when there was a problem with the air conditioning, they tried to charge us to investigate it despite the car being under its 1 year warranty!  Wrote to head office but got nothing more than a standard apology.