I used to do agency Gateline, not platforms but worked alongside some station staff who were agency dispatchers. It won't affect your application with the TOC, if anything it'll have a positive impact if you are reliable and get to know the station managers, also gaining valuable experience in the process. Medical screening is the same as TOC as there are safeguards in place to ensure compliancy with drugs and alcohol and generally fit enough to do safety critical work. Many agency staff do end up with permanent roles with the same TOC they did agency cover for, or for neighbouring ones. I got a permanent job with GTR after doing a bit over 2yrs agency so definitely grateful to the experience I was able to gain as well as connections.
Whether it's worth it for you may depend what your current job is? Agency pays poorly usually minimum wage and mediocre pension contributions and only statutory sickness and holiday pay often included in the hourly rate, so it's worth weighing up with what you are earning now and if you can drop earnings but for the chance to possibly get into a TOC role quicker with the agency experience. You may also not get full time hours with Ontrak, as it will be zero hour contract work, most agencies start you off on less number of hours until they see you are a good reliable worker and then you start to get full time or even more, I was doing 50-70h weeks regularly, covering many different stations so it can be interesting if you get into their good books! (my experience was with Fusion People rather than Ontrak but they cover similar roles)
