If the internet only goes down when its raining then its gotta be an exterior problem thus needs an openreach engineer to fix it. Knowing there is a problem but having to wait for that problem to cause another problem before I can get help is in my point of view stupid.
Bt usually says they will send an engineer but you will be eligible to a fee if the issue is a fault on my end. If the fault is outside of my property then im not eligible so why not book an engineer? Instead of giving me the run around.
Anyhow I'll call them again tomorrow, hopefully ill get somebody on the line who understands this issue and can help get it sorted.
I used to work for BT donkeys years ago so things have probably changed since then but your fault description leads me to believe that a cable jointer has spliced into an underground cable and not sealed it correctly, either that or an old joint is failing