Better first, not ban first
A general principle is being violated here:
A ban on the sale of new boilers will be needed to persuade people to switch to greener heat pumps, the Government’s infrastructure chief has said.
As Terry Pratchett noted about the difference between sheep and goats - one can be led, the other has to be driven. Humans are on the goat side of this divide. To continue mutilating animal analogies, humans will drink if led to water without forcing.
That a behaviour change is desired, well, OK. The necessary action is thus to lead, to tempt, to incentivise, not to drive or ban.
This means that we do not ban - or, sorry, should not ban - a particular technology because we desire that behaviour change. Instead it is necessary to create the better alternative first then marvel as everyone adopts it entirely voluntarily.
When speaking about climate change this does still work. Recall, as the Stern Review tells us, that our aim is to maximise human utility over time. If a ban is deployed then that’s an obvious admission that the action being forced is not utility maximising - which is directly contrary to the aim we’re hoping to pursue.
Make heat pumps - or insulation, or Passivhaus, or solar water heating, or whatever up to and including shivering in the mire - preferable to gas boilers by developing those alternatives first.
That is, make the better way first rather than ban and hope one turns up.