As far as I am aware, it is SCC only. They do corporate and adult training weeks on some vessels, like Royalist and the yachts, so maybe there are opportunities. I know there are undersubscribed weeks but lo and behold, these usually coincide with exams so may be a non-starter.
Make an enquiry through your chain of command. You would think that someone would have already thought about this and you get a quick answer, but sometimes, just sometimes, someone has to think of it first!