Just be aware that lots of UK grass airstrips during ww2 were not just grass, they had Irving grid mating all over them to help make them more all weather yet with grass still growing threw which helped hide them from aerial photos, also they could be laid down quite quickly yet be functional and lots of grass fields were done as auxiliary airfields and were never used especially in the midlands in 1939/40.
A good many of the old ww2 era grass airfields even today if you dug down a few inches you would find ww2 Irving grid mating which I can tell you now from personal experience are a pain to revert to arable use even though it can be quite lucrative in scrap steel.