Hello again Seaton Approach
The last I saw of the AVTECH course was over 2.5 years ago, so I have to accept that I may well be out of touch. I was a user and supporter of AVTECH's Ops courses and the City & Guilds Certificate for many years, however, the course materials became very dated and frankly at that time, Ý felt they were neglecting the Ops courses in favour of other areas of their business (and I told them so at the time). In my opinion the course that I had sight fell short of the ICAO Doc. 7192 D3 syllabus, however, that is not to say it did not have training value.
It may well be that they have pulled their socks up. Whether it has now been revised to meet 7192 D3 I can't say, but I'd be delighted were that the case.
I can however vouch for the GCNS course having had an input to the syllabus there. But course do vary with the interpretation of the syllabus and I would expect to see a few differences between them, but I do agree with you, the basic theory needs covered.