anotherthing
Your points are of course valid, but it depends "where / when / what aspects" you think this incident was "serious".
I will presume you are an ATCO... and to you the incident was "serious" because there was an aircraft wandering around the LTMA that either could not or would not follow headings. To an ATCO that is very serious...
As a pilot, this was somewhat less so... the aircraft had good endurance, and I am sure you guys would have kept things out if it's way, albeit with extensive disruption to other traffic. Apart from "how" they got into this scenario, nobody (crew included) seemed to work out how hard it is to fly a fast aircraft using a mickey mouse small compass, and located far from the (Sby) AI. It was the second ATCO who picked up on this I think and went for the timed turns? Good on him...
Language played a part no doubt, but how many of our "newer" pilots (and ATCOs?) are trained in timed turns / no compass procedures? I've done 12+ years in the airlines, and never flown either the simulator or the aircraft on a liquid compass
As the AAIB observed, having got into that situation, it would require exceptional crew co-ordination to fly accurately - they fact they flew altitudes and altitude changes well shows at least the priority was directed correctly... heading I'm afraid comes a distinct second.
NoD