I'm not denying the cost to you of the fiasco - what you've had to suffer was diabolical.
The problem is an under funded, under resourced, under trained industry through the whole chain from OpenReach through to most ISPs. I believe the significant reason for this is that primarily the major ISPs compete 99% on price and 1% on the service they provide. The inevitable result is that people get what they pay for. The ISPs that do care are then facing suppliers who are conditioned by the attitudes of the major players where suppliers not doing enough is not challenged by the ISPs and the customers suffer.
There are also the accountants/managers at play who only look at short term costs. Your case illustrates this perfectly. At every stage they have done the minimum to keep the costs down. The result has been that in the long term it has cost them far more with your 50 odd visits than if someone early on had recognised that allocating whatever resource it took to get it fixed would cost them less in the long term.
AAISP November 2016
(Previous ISP Plusnet November 2001 to October 2016) Why I left Plusnet
Telephone rental: Pulse8