The problem is the "business model" of airfields in the UK.
An airfield uses a lot of land, and airfields are counted as "brownfield" which means they can be built on. Given the choice between a couple of dozen GA visitors a day, prepared to pay (say) £15 each and (maybe) a few larger jobbies at £100 and (maybe) buy a few hundred litres of fuel (with all the palaver of Government regulation on fuel) - offset by the cost of an A/G operator or a FISO and maybe a fireman or two, and the CAA's and OfCom's charges for licences...
...or sell the site for a few million as building land:
you have to be dedicated to running an airfield. Look back at the number of airfields (even municipal ones) that are now housing estates, and the writing is on the wall.
The USA has a different model: airfields are essential transport infrastructure and are needed, so they are funded out of a central pot. Landing fees? What are they? The USA also has a lot of spare land lying around.
HMG isn't going to fund airfields - they see them as a source of taxation while they're there and a source of more taxation when they change role to building site.
I suspect (with some but incomplete statistics) that there are far more farm strips in the UK than every other sort of airfield added together. That's certainly the case in the little corner where I am. It's the way it's going to go, I suspect.