Jobs done. Used Nylex fittings, worm drive hose clamps and barbed joiners from the garden section (any excuse to go to a hardware store).
Did get caught out though. When I went to show off my fine work both pumps worked when connected but when it was all packed away the external pump didn't. Quick diagnostic showed that even though I used a one way joiner the external pump was able to suck air into the system through the one way valve. Suppose one way really means one way. Simple fix installed an in line stop valve.
Will post pics after Easter break