Aside from all the every obvious safety reasons for having an valid MoT which are outlined above, I have been stopped in Switzerland on a previous 10CR and aside from the usual passport checks they spent some time inspecting the car's paperwork (V5, Insurance docs and the MoT) and we were glad to have the full gamut of paperwork for the car, as I would have imagined we might well have been there for quite some time trying to explain that we don't need an MoT.
The other thing that is of concern to me is that if you are unfortunate enough to be involved in an incident (in the UK or Europe) and you don't have (or need) an MoT and YOU have missed something and your car is technically unsafe how will your insurer react to this? Would you be be personally be liable? Who knows but I don't intend to find out!