G'day Phil,
Yes mate fixed - purchased a new Wema fuel sender. If you have the same issue, make sure you get the right sender:
With float at the bottom it should read 240 ohm and at the top 30 ohm, or
With float at the bottom it should read 0 ohm and at the top 180 ohm.
Here is the one I bought: http://www.wema.com/publish_files/S3_-_326000-326080.pdf . Fortunately it comes with the standard 5 hole configuration as the original.
I purchased the wrong one to start with and when I connected it, it showed full when empty and empty when full
Cheers,
Cam