On hold > 100 mins to discuss ongoing BB fault. No progress.

[#1]

I have an ongoing broadband service reliability issue, the support ticket for which has been closed.
To re-raise it I've been put on hold for more than 100 mins in total. I actually got as far as speaking to a tech support engineer today at about 11:15. He put me on hold too while getting a test report from the exchange.
The call got disconnected soon after he took me off hold.
No there's still no support ticket to follow.
Rather than go through this again I may as well just cancel the direct debit & find a new provider.

[#2]

Don't do that.  If you cancel the service it will be a new install from your new provider, with consequential delays in getting service reinstated and probably cancellation and activation charges. 
What I'd suggest is to re-raise the fault online, if you can do so, and also raise an online complaint to see if someone will take it in hand. 

[#3]

to raise the broadband fault again go to https://faults.plus.net

[#4]

To raise the complaint: https://www.plus.net/wizard/?p=wizard&page=22909&wizard_id=38