...... Is this a bad earth as the battery is okay. ....
Yes, those could be symptoms of failing ground connection in the loom. The main Loom ground connects to the engine case just above the front sprocket. It is a common weak link in the electrical system. It's about a 14 gauge, black/white wire. Follow it back to the loom until you find a single spade connector. That connector often corrodes and overheats. It's best to remove it entirely, and solder the wires together for a more durable and reliable connection.
Also have a look at the large white gang connector between the Front and Main Looms, along with the black gang connector that leads to the right hand switch pod. Open them up and look for wires and terminals that show signs of overheating or corrosion.
There is also a yellow/white wire in the Yellow gang connector leading to the left-hand switchpod. That wire supplies power to the headlights, and it is a problem area. Open up that connector and look for signs of overheating.