Worst service I've ever had from a BMW dealer

Stratstone BMW Harrogate
I've been looking for a used BMW 320d SE touring with the 177bhp engine for some time and saw one advertised at Stratstone BMW Harrogate, a 2007 (57) with 25000 miles on the clock. The 177 engine is 10% more powerful but also 10% more economical than its predecessor, with lower CO2 output & thus lower road tax.
I emailed Stratstone to make sure it was the 177, this was confirmed. Before making the 240 mile round trip to Harrogate, I rang them to confirm - "yes it was the 177"
I went to Harrogate, drove the car, liked it, was reassured again "yes it was the 177", so left £500 deposit and signed a contract.
On returning home with a copy of the reg. document I discovered that the car actually had a CO2 output greater than it should have. After some research I realised that either the document were wrong or Stratstone were wrong. Another email was answered with "We can assure you this is a 177 engine"
I spoke to a friend who works for another BMW dealer who advised that I discover when the car was built. If before Sept 2007 it was not the 117.
I rang again and only after some major pressure did they check BMW's database. The car was made in May 2007 - and was not the car they had offered me!!!
They offered me a £500 discount - the car would cost more than this extra to run with additional road tax & fuel costs. The only alternative was a refund. As I pointed out under the Sale of Goods Act they also need to meet my reasonable costs - they offered me £25 of petrol - but I would have to come to Harrogate to pick it up!!!
My advice: If you want to buy a BMW from these chaps - do your homework first or better still find a BMW dealer that knows what they are doing.
PS They're still advertising the car as a 177 on Autotrader!!!