A hot press is a very small room in which you place a big copper tank.
A worm from the heating system goes in and out of it. The worm heats
the water inside and supplies the hot water tap.

Some people call it an airing cupboard.

So it is this tank that is not heating proberly.

Thanks for the reply

Any suggestions

Robert
Please explain what you mean by the "hot press". It's not a term I've come
across!