how many hours is a week, if I am trying to work out pro rata earnings backwards?

[MegReally]

is it 37.5? 40? any ideas anyone? I can't seem to make sum work

Depends on the company Meg, they can all be different. I've seen 'f/t' hours defined as anything from 34.5 to 40. You'd have to find out what is in a f/t contract.