The Fuel gauge hasn't worked properly at all so far, initially I thought it was due to no fuel in the tank but theres a good 5 litres in there now and not a flicker from the gauge.
I worked through the circuit methodically: Sender, loom, dash connector, dash loom, guage - and s*ds law the issue turned out to be the loom connector to the gauge - the very last part I tested. The pin wasn't inserted all the way home in the gauge socket so not giving the gauge a good/any signal.
Easy fixed once found though & with the sender out of the fuel tank I could fully test the gauge over its whole range.
I'll re-install the fuel sender in the thank & then its good to go. Minor problem solved.