Pulled out the Perana tank today as the sender wasn’t working. From day one I’ve had issues with rust in the fuel filter and I’ve been through a few.
The inside of the tank to a quarter way up is rusty but top half is fine. I’ve put some vinegar and water in to soak for a week maybe two which should fix that. I do have another tank I had properly cleaned at a radiator and tank refurb company which I’ll probably replace this one with after I spray it up.
As for the sender I presume it was working but the fuel float has cracked and is full of fuel. Senders resistance reads ok after cleaning all the crud left inside out.
So question is anyone know how to get a new float or a replacement idea.

I've got a spare fuel tank sender unit from a 1600GT, should be the same and appears to be in workable condition. PM me if interested. Cheers, Terry

I got one from an instrument repairer many years ago.  I remember being surprised that it was a standard off the shelf float so possibly still available from these types of repairers.