Thanks for your help everybody, managed to find an 'essential journey' yesterday to take the bike out, and check through the various jobs I have done on it over winter, all good, and the fuel gauge reset itself like people said it would.
Onto the next challenge of setting the bike up for myself, waiting for Tralex's crash bars to arrive, apparently there is an Brexit issue with Courier, so a waiting game I guess.
Did find 1 other problem, which I will post elsewhere.