Roger Mills wrote

However, there may be some times when I don't visit the flat for more

than a month - so, with monthly billing, I may sometimes be unable to

make the requisite number of calls.

Last time this came up somebody suggested use of a BT telephone charge
card the charges from which counted as chargable calls.

Has this now vanished ?

Suppose you have Call Minder with a text message, chargable to your
bill, every time a message is left. That should work but Call Minder is
charged at £3.15/ month.

Some answering machine phones may have an equivalent feature.

The poster's insurance company would probably be happier if there was a
monthly visitor and they could make the phone calls to confirm their
visits.

Any other ideas ?

--
Mike D