[Damien]

A bit of a report back for anyone interested.
The problem surrounds the sender being fitted in the tank and not wanting to work as I have connected 2 new and one old senders which all worked whilst connected into the cars system but outside the tank, but once installed in the tank, only the crusty old sender works. Needless to say that sender stayed in the tank. I thought the new senders may have been grounding out in the tank somehow when fitted, so I played around with the power strap off the sender to make sure it wasn't touching anything but it didn't seem to make any difference. Anyhoo, the crusty old sender stays in for now and I will look to find another OEM sender that I can have rebuilt to install at a later date.
Cheers.