this is the challenge that OR has with the exchange clousres. Some who can get fttp just won't move (some obviously has equipment that isn't upgradable and thats semi understandable)
And hence the "stop sell" on new orders, migrations, and modifies in certain areas. As soon as someone moves out, it forces FTTP on the newcomers. Ditto if the existing occupant wants to change ISP or change speed.
After a few years, natural churn will get rid of most of the copper users. The last remaining few - well that's what the exchange closure trial is all about, how best to mop them up.
If you tell people they have to pay more to stay on copper, I think that'll make most of them move. For example, if you tell people they have to take FTTP to recontract, and conversely if they choose to stay on copper, they pay out-of-contract rates.