It’s not too difficult to wild camp in England. We’ve been successfully doing it years! Never been moved on or had any problems. You just need to know where to look. There are also apps which are quite useful. I wouldn’t stay on a campsite if you paid me, urgh.
We use a microbe/ green fluid in our toilet so it can be emptied in a normal toilet. We’ve never had problems topping up the fresh water tank (it’ll last us 4 days), again you just have to know where to look for taps and have a selection of adaptors to fit any tap. We’ve got a solar panel (a must) which keeps the leisure battery topped up. We had one of the gas bottles replaced with a refillable one, so can top up at garages with LPG. It’s significantly cheaper than the cost of exchanging a gas bottle (also handy for abroad - each country has its own different bottle, so you can’t exchange). I would highly recommend this - it paid for itself pretty quickly. It was either Gas-it or Gas-lo who did it - whichever was cheapest.
As for width/ length a problem - not really. It’s down to the skill of the driver actually. Ours is just over 7 metres long, just over 3 metres high. We’ve never had any issues. We also live up a narrow, steep lane and it’s stored on our drive. If you think that bin lorries have to access most roads you’ll realise it is the skill of the driver that is important. We have a much smaller bin lorry where we live (narrow lanes) and it’s slightly bigger than our van. Roads are well signed with height restrictions.
I’ve nothing to add about costs as someone upthread explained that very well.
That is completely unrealistic if you only plan to use it 2 weeks a year. We get 2 months a year, in total, away in ours (not all in one go as we have to book annual leave/ DS at school). Vehicles - especially heavy ones do not like to be stood for 50 weeks of the year. It’ll cause damage.
It cost us 33k to buy, keeping it on the road (MOT etc) and diesel all add up. We could have some very nice holidays on that money. I’d hate that though. I bloody love having my home on wheels to holiday in. We’re cyclists (MH has a garage) so it is ideal for us. There’s nothing like pulling up in a stunning spot, gorgeous views from every window in peace and tranquility in the comfort of your home on wheels. Then moving on the next day, and the same, and the next day etc. I couldn’t bear being hemmed in on a campsite and being charged 30 quid for the privilege. I have never felt settled or relaxed in a hotel. I couldn’t cope with packing a suitcase!! We literally Chuck everything in the van and don’t worry! Books, games, bikes, toys, stacks of clothes. We don’t mind self catering either.
You also need to consider the cost of buying a MH at the mo. The costs have shot up over the past few years. If you bide your time, I’m sure all the folk that bought them and haven’t got on with them will be selling at some point!