I live in a big arable farming area OP. The land here is ideal for growing the typical British arable crops of wheat, rape, oats, and winter barley, peas, beans, with some others. Its hideous.
To maximise yield per acre, all the farming is contracted out to agricultural contractors who have giant machinery. Said giant machinery doesn't do anything but straight lines so all the corners are just left to do nothing and that means they are sprayed to death with pesticides and weedkillers. The hedgerows were dug up years ago to maximise yield and most of the traditional footpaths/bridleways were ploughed over or diverted to the most inconvenient spots so they are no longer used because they are so overgrown.
No wildlife is permitted to live here. There used to be deer but they have been shot. All "pests" are shot regularly, such as pigeons. Theres also trapping going on, illegal or permitted, it happens. I think that theres some arrangement whereby people are allowed to shoot or trap for sport and are permitted to do it free of charge or for a small payment. Its all quite secretive. Anyway, nothing lives here.
Its like living in an arable desert. There are individual farms but the owners don't farm themselves any more, except for a few historical leases to people who rent the land for their own sheep. There were literally two fields where that went on and last summer one of those was ploughed up and the other is unused and full of weeds now. There is one local farmer who farms his own land (by some miracle its a mixed arable and grazing farm) and I am friends with his farm labourer, and I often think he is the last of a dying breed. He has lived in his tied cottage and worked on that farm all his life and will retire there. He isn't being replaced.
The monotony of the scenery here is actually dreadful and quite depressing. The land is in crops all year round with I think every 3rd winter off. Every last ounce is got out of the land here, and its pumped full of fertiliser and additives and weedkillers to do so.
I know if you live in a modern housing estate, veganism sounds like some kind of great solution but in reality it isn't. The UK has a high population because it lies in the middle of a climate zone which pre-disposes to mixed farming and can produce a lot of food than drier or colder areas. It has good, mixed soils and prime beef can be reared on those areas and sheep and deer on its higher land.
What I'd actually support is more forestation and public access of non-animal farmed areas for recreation because much of upland Britain isn't a natural environment by any means and the lack of tree cover increases soil loss and acidity, meaning nothing can grow. Theres a farming initiative to encourage young people into farming and smaller farms, because the trend is increasingly towards mega farms farmed by contractors who do it as a job and who have little relationship with the land because they don't live on it.
The UK isn't that bad for farming animals compared to most countries because we tend to keep them in for shelter and food over winter and turn them out in summer. In many countries, cattle, sheep and pigs are in all year round.
Also bear in mind that not all arable land is suitable for all arable crops. Potatoes for instance require a very particular climate and soil type to grow well and can't be grown everywhere. So a smallholding looking to be self sufficient would likely be deficient in certain nutrients from certain crops and would have to trade with others IYSWIM.
The UK's best naturally growing crop by far is grass. The UK produces wonderful, nutritious grasses that can easily be made into enough hay to sustain grazing animals kept indoors over winter or supplement outdoor grazing.