go over to
https://www.navitron.org.uk/forum/index.php and have a read. Pretty much the home of off grid folks in the UK. As Mudsticks mentioned, you're biggest issues are going to be finding a plot and getting the relevant permissions. Doing something similar has been my dream since I was a teenager but the sort of building I wanted just wouldn't pass planning.
Earthships, while lovely, won't get planning in the UK, there's only two and they're demonstration buildings that you can't live in. Very interesting though. Look for a film called Garbage Warrior, which is about Mike Reynolds who invented them and the struggles he faced along the way. Likewise look at earth bag building promoted by Owen geiger, plenty of stuff on YouTube as well. Oh for the open spaces of America and counties which don't require building to code.
There's a bunch of off grid and timber framed houses on Grand Designs if you look through their index. Ben Law's build is the most famous and very similar to what I designed for myself 30 years ago except I wanted to use post and beam, not cruck framing.
Going off-grid is very much a state of mind. Everything about the house and your needs must be rethought in relation to it. If you still want the modern toys of computers, internet, big tv and stereo etc, you'll need a big battery supply, which means a need to charge it whatever the weather. PV is so cheap now, put in lots, but it doesn't work if we have typically British weather.
For heating, wood is great but only if you're home all day to stoke the fires, have a woodland to feed it and about 2 solid months each year to cut, move, split and stack the wood and the space for 2-3 years worth of it as it dries. This is how I heat my own house as we have no central heating. Wish when I renovated this place I'd dug out the floors and put in underfloor heating and a ground source heat pump, but that's expensive and needs mains power really to run the pump.
The absolute biggest thing you can do to make a house affordable and buildable is to design it to be small and insulate the heck out of it. An alternative would be to look for a place in the country you can buy and then renovate, which is what we did over the past several years. Stripped to bare shell, new windows, doors, new upstairs floors, new render inside and out, new wood stoves for heating, 6kw of solar on the roof, solar diverter for hot water, we have 7 acres of old woodland which heats the house and we work from home so we can light the fires first thing and keep the place ticking over all day in the winter.
Consider also building partially off grid. Get mains power in (it might cost £20k but worth every penny and about what you'd spend on an off grid system) but be off sewage and water grids. Rainwater capture is cheap and pretty reliable here and perfect for washing machines and flushing toilets which waste so much clean water. Sewage can be treated with traditional septic systems, reed beds, modern treatment plants or you could go the composting toilet route.
Looking at the bookshelf next to my chair as I type this, here's a few from my library to get you started:
The woodland house - Ben Law
roundwood timber framing - ben law
The old house eco handbook
Small homes, the right size - Lloyd Khan
Serious Straw Bale - lacinski and bergeron
Building with Straw Bales - Barbara jones
Building with awareness - ted owens (very good book on building a small modern off grid home cheaply)
The renewable energy handbook - Kemp
Cabin Porn
create and oasis with grey water - art ludwig
building a low impact roundhouse - Tony wrench (for information about how difficult building off grid is from a planning point of view)
The timber framed home - Ted Benson
Build a Classic Timber framed home - Sobon (definitely get this one)
Little house on a small planet - Salomon
Tiny Homes, simple shelter - Lloyd Khan
The good life - Helen and Scott Nearing