Hi,
You might take a look at:
CAP 793: Safe Operating Practices at Unlicensed Aerodromes | Publications | About the CAA
This has the essential info you need to safely operate an unlicensed aerodrome. Any bit of land (or water!) used for taking off or landing an aircraft is called an aerodrome, even if it's someone's back garden.
Cheers,
TheOddOne