Schedule 15 says:
Persons residing or staying with person subject to service law in designated area
8A person is within this paragraph (subject to paragraph 11) if—
(a)he resides or is staying with a person subject to service law in a designated area; and
(b)he is in that designated area.
I read that to say that if you are in Dhekelia or Episkopi etc or any designated area you are caught by the Act.
I would suggest that doesnt mean random civvies popping in for a visit. As I said Army regs do not supersede host nation laws unless there is a prior agreement, would a kraut visiting his sister who is married to a soldier in Gutersloh come under the authority of the British military police? I think not.