Definatly earthing mate...the wiring does not change, ie no one would have swapped the wires, give the battery terminals a good clean, and any earth connections to the body of the car, also give all the globe holders a clean, and spray with wd40 and wipe with rag to get most of the excess wd40 off, also make sure you have the correct gobes with the correct power ratings, and all will be fine.

You can check the power rating of the globes in your owners manual, do not go of what was in the car as someone could have fitted incorrect globes.