I went to CATS and can recommend them (residential some years ago). I popped in to their new offices in Luton to say hi a few months ago. They were running training on that day and were very busy, so I sat in on the class for a bit reminiscing about GNAV
. Quite a complex subject for me as a non-mathematician, but made easy by CATS guides and instructors helping me through.
I cant believe the course price hasnt gone up from what I paid quite a few years ago too.
Have fun and enjoy the learning experience!