Farmland is ~69% of the total area of the UK with it being quite stable in the last decade, and most of that being grassland. Solar accounts for ~0.1% of (former) agricultural land, and after 2030 it should be around ~0.6%. The Land Use Framework aims for 1% of land (mainly agricultural, so ~1.5% of ag) for renewables by 2050. Housing doesn't have as comparable figures, but I'm envelope mathing it to about 1.5% by 2050 again. Which makes 3% of ag land, of which crops are roughly 1/3rd, and google says 60% of solar is on good crop land. So a reduction of up to ~6% at the top end.

There are a few flip-sides here - things that many don't like to hear or acknowledge:

There are alternate diets that are suitably nutritious that are achievable on this land, largely by reducing meat consumption. Meat production uses much more land than other food sources, and a lot of that is input crops. Its inefficient. A change in diet can make the UK self-sufficient on much less land.

Solar is a developing technology; it will improve, requiring less land for the same production. If long term trends push up the value of crops and down solar production, the panels can be removed and crops grown instead - its either/or but it is reversible. This is especially important for bringing in non-solar power sources which take longer to realise (nuclear, tidal). I will also note that solar farms are built on the good crop land because it is convenient and the price is right. We will see south facing hills covered soon enough.

Housing and social housing are the same problem; where housing prices are so high compared to salaries, social housing demand increases. Building houses - any houses - solves the problem. The question of density, location, style is a question about what kind of problems we want in 10-20 years time. High rises did not work well at all.