My builder is installing a combi boiler hot water/ heating system in a
holiday flat that we are planning to let out. He does not appear to be
fitting a room thermostat or any sort of timer. Is this normal for
such a system?

I can understand not having a room thermostat as all radiators (except
one) have TRVs but the lack of a timer concerns me. I don't want
enormous bills because the heating is on 24 hours a day.

Can anyone please advise me on what is normal?

Thanks

Jonathan