I'm no expert on UK energy pricing, but the main difference between a boiler and heat pump is that heatpump can be, eg "500% efficient" - a COP of 5. So even if a KWH of energy is 2x the price for electricity a heatpump often comes out ahead.

Electricity in the UK is often 3x or more expensive than electricity for the same energy content. We have some of the most expensive electricity in the world.

COP of 5 when running in perfect conditions (load, EWT temps, variable stage compressor, infinite heat sink/source). You might want to research how realistic constant COP of 5 really is.

Yeah a COP of 5 is very good. 3 is much more typical.

And OP is right. When I've looked into it you aren't going to save any money going to a heat pump; in fact it will likely increase costs slightly.

So it really only makes sense to do when you need a new boiler. If you don't, it makes way more sense to get solar because that's also good for the environment but actually saves you money.