I remember bringing a reconditioned London Taxi engine back from England to Mandello for an Italian friend. As usual I came through Switzerland as the van was empty (apart from engine). At the Swiss/Italian border the Swiss officials were baffled as to what duty to impose and kept asking where the rest of the vehicle was
Had to leave engine on pallet with them to be sorted by my Italian friend the following day. Fortunately the border was not too far from Mandello.
That probably happened because you did not do a transit customs clearance on entering Switzerland at the French/Swiss border.
Have to import car then take it for MOT test equivalent before being able to register it in switzerland
Yes. I have been looking it up, this is the problem because despite the fact that Switzerland is surrounded by the EU it is not part of the Customs Union and apparently doesn't trust the validity of EU conformity documents.