Hobbsy, there is quite a difference between a European diesel and The davis conversion that has been copied by RJL and the late Irvine Diesels.
A classic diesel has the contra piston fitted into the top of the cylinder, this is one of the reasons for the slow warm up and fiddeling with the contra piston. There is quite a lot of mass to heat up to allow the timing to advance. The davis system is an advancement in that the head get all the heat and warms up quickly, the contra piston being in the head doesn't detract or impede heat transfer, in fact it makes for a cooler running diesel.