The issue is lots of renewable generation far from places where it is used and not enough transmission capability.
This is called curtailment and is really, really bad. Energy providers need to pay the windfarms for the energy that they (the grid operators) fail to transmit to where it is needed, and they have to pay backup generation (usually gas) at the place with the load.
You have an intermittent power source (wind), far removed from where the energy is needed, and you do not have sufficient electric transmission capacity.
Heat pumps or EVs far removed from the source of generation will not do you any good. You need load where the energy is produced or you need more transmission capacity.
The situation GB has is that there is load, and there is enough renewable generation on the grid to meet that load, however they do not have the capability to bring the electricty to where the load is. You can lessen the demand, but the generation would not get less through that. The only benefit of that would be that you wouldn't have to spin up gas plants, but the same amount of wind energy would still be lost.
E.g peak solar is around 2pm, peak demand is around 7pm
Grid storage (including EVs and smart heat pumps) absolutely help with this second problem