Tankie, If you find yourself heading North Devon direction, you'd be welcome to try a 2 seater bench out of my V-Class in your MP.
They are blooming heavy though, so it is not something you would just "pop in and out", does need a bit more consideration and a two person lift and ideally plenty of maneuvering space. Lot easier in a V-Class with twin side doors. They're also very bulky to store when not fitted.
The V-Class 2 seater benches also have 3 lumps of metal on the left hand side to allow the single seat to hang off. These protrude 65mm to the left from the centre line of the rail. Worth checking that they wouldn't interfere with the cabinets in the MP.
Clearest view of the 'lumps' is about 2:10 in this >
Cheers, Pete.