I've not seen the EASA notice, but can you help me to understand how
the CAA one permits a positioning flight? Does "must not be flown" (2.1a, 2.1b) mean something different to the interpretation I'm giving it?
Good question.
The CAA's initial announcement of the restriction on its website and its Twitter feed (both still up) say specifically "[we have] issued instructions to stop any
commercial passenger flights from any operator arriving, departing or overflying UK airspace." See
UK Civil Aviation Authority statement.
I agree that the Safety Directive (which I hadn't seen) appears not to allow any flights at all (even though the EASA Emergency AD does).
I guess the proof of the pudding will be whether that TUI Max 8 does in fact position back to the UK.