Blowesy
If you’re serious, I wouldn’t bother with a course at all(just need to check some of the posts on here to get an idea as to how useful they are), just start applying to the ROV companies.
With your background, and electrical training, there’s a good chance someone will offer you a job.
Something you should remember is that most of the big ROV companies started out as Dive companies, so much of the management are ex divers, LSTs, etc. Meaning some off them are baised towards ex-divers, especially ones who have bothered to go and get some electrical training.
One thing though. They’ll offer you a trainee rate. Which is pobably going to be a damn sight lower than a sparky would earn onshore.