Hi Speedy G

My Fuel light does exactly the same as yours, I only had y tank out last week to fit an 023 pump thinking I could check everything and sort tha problem at the same time. I measured the resistance of the sender unit and it all looked ok but still got the light on most of the time but the fuel gauge works perfectly

Damo probably got it spot on, replace with new unit to fix

Cheers Malc