We went from a 21' to a 18' losing a garage along the way so we bought a back box, we now have a 21' again. DOH. Worse MH decision we have ever made.
We would not want to be without our garage for 2 bikes, maybe a scooter later in life. Better than hanging off the back.
But we also would not want a 'van' cab compared with our 'A' Class with panoramic screen - great for viewing mountains which we like.
We also appreciate the king-sized fixed bed and seating at dinner for 6 when we want that.
Result is that to have those things one needs 7m. Also we like the quality, and most quality builders do not do anything much smaller than 6m.
As for driving, having driven 7.5t trucks and taken them in some tight places, including lanes in the City of London, it does not phase me. Parking is less easy in some towns, but more so in UK than Continent where we do 95% of our touring. Aires and wildcamping are not problems and much bigger MHs do it.
Overhang just needs more care/angling, but back end is protected by towbar(not that we tow)
It is horses for courses and this horse is pedigree for us.
As for initial cost, when buying at 6 years old and privately there is not a lot of difference between our N+B Arto 69(£27K at 16,000 miles) and smaller/cheaper (at new) MHs - they all have chassis, engine, shower, toilet, cooker, fridge, water and electric systems, which all cost - just a bit more bodywork, which is not so expensive because the labour cost to fit a 7m or 5m side panel is the same. The first 5 years depreciation is the steepest. I suggest good quality PVCs at 6 years will not be much under £20K. I am happy to pay the difference for the space.
Geoff