I just got back from seeing one of the UK's top ENT surgeons and have been told that my ETs are fine and I do not have a blockage / glue ear. He reckons that my issue is an inner-ear problem. He was pretty adamant about the ETs - and it didn't take him long to decide.
So, it appears that my time as a "Google Doctor" has not paid dividends...back to square one...
Anyway, I doubt I'll be contributing much more to this thread - I do hope the links I've provided help someone.
BTW - The ENT surgeon told me that "Laser Eustachian Tuboplasty" was pretty much a scam in his opinion - unlikely to do anything except drain your bank account (I had a quote - think 5-figures Sterling...)
Take care y'all.