NDW,
before you do a training course, you need to think about where you are going to get a job from. The "air observer" and similar courses train you to have some familiarity with heles and a little about flight ops. However, there are no jobs for people with just that training.
In the UK police observers are usually police officers or they are non-police, but trained by the individual units. Similarly HEMS crew are experienced paramedics. There are one or two jobs as observers doing things like pipeline or overhead line survey. These jobs are generally given to people with pipe;ine or overhead line knowledge.
The "observer" but is a secondary part of the job role.