So, I rate myself as having almost zero knowledge of how cars actually work and go together but due to HM Revenue and Customs messing up I have an unexpected windfall and feel it would be best directed towards a Gruppe M. Could someone give me very clear advice on whether I could buy one off the shelf and get a normal garage to fit it for me of would I need a specialist fitter? Advice on best places to source one would be welcome too. Thanks.