Thanks for the reply Steve. I did initially take the vehicle in at the end of Feb, where they had it for two days. It went back in at the start of July because the new roof had arrived, hence my frustration at them telling me they are still talking to MB. I love the vehicle, but I've lost a lot of confidence in this dealership and the brand sadly.The whole warranty process takes a lot of time unfortunately and it seems that a lot of dealers aren't used to processing Marco Polo specific areas, i.e. the roof. Also they can be ignorant of fibre glass panels and any associated paint issues. I guess this is all understandable, however.... It really isn't efficient service in my opinion. What they could (should?) have done is process all the groundwork and paperwork necessary before taking your vehicle in. My resolution took many months but initially I took it in and they took details and photographs of the affected areas. The warranty process was drawn out but maybe irrelevant given the unavailability of new roofs. When the roof finally came in it was boxed and sent to their bodyshop for painting and only when it returned to the dealer the booking made to bring my vehicle in for fitting.
My suggestion is that you arrange to recover your vehicle (check that they have all the evidence that they need in terms of pictures, chassis numbers etc) and then ask them to ring you when they have a (painted) roof in their workshops and can book you in for fitting. Relax, be patient, you will still have use of your MP and it will get sorted (eventually!!)