Car would'nt start Sunday morning!!!! The engine electronic's fault light came on. She started turning but no voom!!!!

Managed to get her going after spraying a bit of WD40 on the battery terminals, however she sounded rough for the first ride afterwards. The only link I can make is that the low coolant level indicator came on. Filled slighty over the cool mark, (about 2 cms over)..... surely there's no link to this.