If it's a microlight only site, it's probably unlicenced and hence no ATZ, so theoretically you can do what you like provided you comply with rule 5; that doesn't absolve you from compliance with 'knowingly or deliberately hazarding the safety of an aircraft' in the ANO (both yours and theirs).
Microlight common frequency (limited to use for microlight associated comms only) is 129.825; why not try calling? It should only be A/G radio and the radio operator is not allowed to issue instructions or advice, only traffic information to allow you to conduct your flight in safety.