What is the reason? Is it just to pay someone to switch the lights on and off again, or does there have to be a fireman etc?
The answer to most UK aviation regulatory matters is
here.
I saw a Pilatus PC-12 at Compton Abbas last Friday. As you might know, it is not the smoothest strip in the world and I was surprised to see one there. However, it took off quite happily in half the strip.
Sure; I have seen a TBM going to grass strips too. It's OK, but I did say "most"
The grass needs to be solid.