@batpred 

If it needs a battery to ensure a good outcome with a heat-pump, then the hurdle gets even higher as now the home-owner needs to find the £10k+ for the heat-pump, and currently the best part of £4k+ for a fully installed battery and the space for all of this.

It's going to need a re-think, I suspect after much unnecessary delay and time wasted, that the UK will end up where other countries with heavy use of gas heating like the Netherlands and Italy are - a more pragmatic approach, of full heat-pumps for new builds and homes where they're suitable, and hybrid heat-pump systems as retrofits to existing properties - take out the old boiler, install a new hybrid boiler with an outdoor unit, leave the plumbing largely the same. Or like some of the Dutch systems, plumb a heat-pump into the central heating loop and retain the existing boiler for cold weather and instantaneous hot water. 

@temperature_gradient 

Yes, but while a battery needs no maintenance and little space, the hybrid system with all that comes with keeping the old gas boiler (yearly maintenance and space) does not seem to be a large scale solution to me. 
I think our concept of subsiding to get rid of the fossil fuel is better, even if unlikely to be affordable at scale. Still think that making people pay for the emissions will be the best way to get more of us to feel ownership for the emissions we can control. 

@batpred 

Look at what makes heat pump installations difficult - you need a new, typically quite large/larger cylinder, significant replumbing of the hot water system, radiators need replacing, you may need an electricity supply upgrade. You may need your central heating pipework upgrading - there's millions of home with micro-bore, the smaller sized copper and smaller plastic pipes, that will be locked out of heat pumps unless they rip their homes apart to re-plumb. Most of that cost and hassle is eliminated with a hybrid, yes it's not zero carbon and there's still the boiler, but it's a sizeable cut typically 70% in gas use compared to sticking with a gas boiler.

With the average heat pump install costing around £13,000, if a hybrid system can shave £4000 off by avoiding the cylinder, hot water replumbing, new primary pipework, new radiators, that would pay for decades of boiler servicing.

It's classic case of making the perfect the enemy of the good, by demanding nothing less than full, zero carbon heat pumps with all of the cost and disruption, its slowing the transition away from fossil fuels and cutting carbon emissions.

We need to get heat pumps established as a normal, routine way of heating your home and the best way to do that is to take away the risk of moving to something new by having a bridging technology, to get people to start moving across on mass.

Posted by: @temperature_gradient

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Look at what makes heat pump installations difficult - you need a new, typically quite large/larger cylinder, significant replumbing of the hot water system, radiators need replacing, you may need an electricity supply upgrade. You may need your central heating pipework upgrading - there's millions of home with micro-bore, the smaller sized copper and smaller plastic pipes, that will be locked out of heat pumps unless they rip their homes apart to re-plumb.

I know it is not as simple as going from a fossil fuel car to a BEV, without the hybrid.. which we did.

Everybody’s case is different. We did insulation, so we found we only needed to upgrade 2/14 rads for the asho. And those are a doddle, by the way. 
The cylinder is the main point of debate at our home. I think due to thinking it would need to be warmish, but we know the R290 system can warm it to normal temperature.. so not any hurdle. 
The electricity upgrade is a free thing the DNO does. In our case, it was essentially a check, well before we got the BEV. 
A very small percentage of homes need replumbing. Some could probably add A2A.. and keep the boiler running, for a smaller cost. But who would even considering doing this with gas at 7p/kwh? 
By all means if the boiler needs keeping, the ashp can just be added. I see many brands are preparing for a post BUS UK where houses with space may want to keep the gas boiler…