Muffin,
Is your HLS marked on aviation maps? If not then crews will have other things to be looking at rather than seeing if every piece of real estate has a huge white H on it. That is not said to sound flippant, I mean they actually genuinly do not have time too look for every eventuality that might happen on the ground.
It's difficult enough with horses, avoids, chicken farms, farm strips, heli avoids, LFA boundaries, etc. etc.
The best piece of advice I can give you is to speak to Odiham AND Benson, Middle Wallop, Yeovilton, Wattisham, Dishforth, Culdrose Ops. The easiest option is probably AIDU at Northolt to have you HLS marked on the latest maps.
I hope this helps.
HG