Yes, that was a big deal back in the day, which was the main reason one of the engineers (an actual engineer with an engineering degree) at the Centre for Alternative Technology was fairly anti ASHP when we discussed the matter 10 years ago. I looked at some more recent literature and it seems that is less of a problem with modern design.Cheaper anyhow whatever about COPs, another factor I rarely see mentioned is defrosting which is a significant factor in running costs especially around here with relatively high humidity levels.
I suppose the logical thing is that if conditions mean defrosting knocks the COP to less than 1, then you switch to resistive heating.
The point was supposed to be that heat pumps would be used with a very high level of low-carbon electricity and a retro-insulated building stock, but that doesn't seem to be happening. Onshore wind is half the cost of offshore, but a number of counties are very against, so we're paying the price for that.