We are having similar problems Paul, except ours is when its damp! If you can wait for the mods to contact you I'm sure you'll get the help, they are trying their best to sort our issue out.
Had the same thing ringing BT in India, they just about called me a liar and I really don't appreciate that type of behaviour at all.
I had the same, basically called me a liar, even though the BT engineer himself told me there are numerous people connected to the cabinet with the exact same problem & he is sick of being sent to the same addresses over and over again with the problem never being resolved.
If the engineer is sick and tired of it why has he not done something about it. Is it not his job to resolve faults and if he/she is not capable of doing that he should report it further up the line until somebody who can resolve it does.
He's been to me three times, each time hes tested my equipment, the line and confirmed everything in my home is ok.
He's then sent his report to whoever he sends it to and nothing seems to get done. when the problem has not been resolved i call tech support again i get messed around for days on end then they make another appointment for the same engineer to come to my home do the same tests and submit his report. It's ridiculous. He took it further, apparently he was frustrated and looked for help on a forum for bt staff and that's how he got somebody to meet him at the cabinet and change the card. Can't fault the engineer.He's the only one in this whole saga who has been helpful.
As you have now been offered the help of moderator, I would leave it to them and don't involve customer services again. The moderators will contact you and keep you updated with what is happening until the problem is resolved.
Now I have no connection at all. Normally this time of the morning I'm getting around 0.50 but now I've got zero connection.Blue light on my HH5 but all my devices showing no connection.Rapidly losing patience.Ridiculous.
Finally, issue seems to have been resolved thanks to the engineer who visited me three times.
Asked for help on a forum last week and another engineer contacted him, they met at the cab friday and changed the card.That didnt work so they went back to the cab yesterday and finally found the fault.As soon as they replaced the faulty component at 6pm last night my connection was and is still flying. 7 weeks of hassle and if it wasnt for the engineer using his initiative this issue would have probably rolled on for another 7 weeks.