Sorry for loads of posts, am a new owner and value the fact that i can pick your brains!
fuel gauge sits on empty when the ignition is off, and when its on goes up to a 1/4 of a tank regardless of how much is actually in it, would i need a new sender unit maybe?

Yes, it goes to zero when powered off, and yes you are correct, the cause of the 1/4 tank is most likely the sender unit, either the float has fuel in it or the unit is simply going bad. They last quite a while, some up to 30 years it seems!

ok ill take it out and have a look, thanks for your help