HI Dominic
As John says they are Michael Jordan specials, they used to be based on the Aventura, now the Vogue, they are usually cheaper than the original when new and have extra kit added. We have had both Expression and Impression, the latter is now discontinued but was even better specced based on what was the Vogue GTS,both the vans we had were very good only problem on one was a leaky tap that was fixed under warranty. Some people say that the dealer specials are more difficult to get spares for if you need upholstery or decals etc. The rest of the van,say fridge, heaters , toilet and shower are the same as the Abbey.The Expression has been around long enought to feature in Glass' Guide as a model in it's own right.As for Martins I can't help you I am afraid.