Found a good to do thats easy and anyone with limited knowledge can do... I replaced my battery for a bosch s5 but I also took out the battery tray and noticed that all the earthing points under the tray looked corroded and blue.

so I simply got a bit of wire wool and fine sandpaper and got them back to being shiny... theres a main earth point and two smaller earth points probably for headlights etc... then put them all back with copper grease to stop them going blue again..... also did the connection to starter motor and alternator.

results brighter headlights, quicker start and sounds healthier also idle felt quieter. some of that will be down to the better battery but worth doing as it's only a 30 job for next to free

you can get battery grease from your local motor factors, stops oxidation on the terminals.

 

hth