Re: ransom fees and copper cables
(1) If I do as they want, ie end my POTS/ADSL service, they will charge me a "cease" fee, as if I were the one in breach of contract. If I don't do it, they will breach the contact.
If you choose to terminate your POTS/ADSL service early then you will have to pay a cease fee. It's not a breach of contract but it is your choice not to continue for the full term and your provider has a right to compensation.
But who is wanting to end your POTS/ADSL service? BT don't. BT will continue to provide whatever services they can over whatever cabling is available to your property. This article is talking only about the voice service and BT (or whoever your current provider is) will just help you move over to a VoIP solution. This will work fine over ADSL.
What is OpenReach doing to replace these ancient cables?
They are replacing them with fibre. Currently 85% of the country is covered, more is being added at rapid pace. However that process is not what this article is about.
Why can't I continue having my Internet service over the copper wire that is perfectly good enough?
You can. At least for now, likely for several more years, even if/when you have fibre available. There will eventually come a time when BT will force you to switch to fibre (at no cost to you) but for now they have only vague plans as to how that will happen and it depends on the fibre availability at your exchange.
The bottom line here is that you should stop panicking. You don't have to do anything other than work with your Communication Provider to get your voice service switched over to VoIP. It won't cost you a penny.