Hi Bob, Thanks for the reply and I apologize for my lock of knowledge.
There was water flow with the old pump which must of still let water
through when it was off somehow when the new one does not. When I
turned the mains off and drained the cold tank there was flow until
the tank emptied.

What will connecting mains water do to the hot feed ? and do you mean
turn the mains back on which will cause the cold tank to fill and then
connect a mains supply to the shower head.

Again sorry if I am asking a stupid question but If either the hot
feed or cold feed has an air lock, wouldn't I get either just hot or
cold. ?

And should I worry about the warnings of installing it in the loft ?.

Thanks again
Spence.