Thanks Chuck, I have been leaning towards this solution while being
incredibly inactive at work today. Your suggestion of using a hose will
mean that I can really reduce the bilge level.

I have a very serious mechanical bilge pump which a previous owner had
hidden behind a bulkhead (that was a surprise I can tell you). I may
just use this instead and mount it in the transom and place a through
hole out the back of the stern.

The intake hose will be long though, can this be a problem? From what I
have read, it seems to be more important that the outlet hose is short,
which will be with this solution. Will I need to mount a non-return
valve on the intake hose?