Generally not taught on the PPL? Please tell me you are joking or misinformed.
I wish he were. I have encountered many pilots unable or unwilling to use a sideslip, including instructors. May be different in the UK, and I hope it is, but here in France one of our club aeroplane instructors will reluctantly admit that I can sideslip if I want to, but not if he is on board. The other doesn't mind, but doesn't teach it to his students. I instruct on three axis microlights, and my students learn sideslips, straight and in a turn. Oh, and s turns, and anything else likely to help in the event of an engine failure or a Bu**ered approach where no go-round is possible. Quite a lot of hill sites for example.