From January 1st 2022 all wood burning and multi fuel stoves sold in the UK must meet Ecodesign standards by law. So if you are thinking of upgrading this is a crucial aspect to consider. It is all part of the govt green air strategy.
There are no penalties at present for homeowners who already own and operate an older stove that is not Ecodesign compliant. You can still sell your home with no extra penalties if you have an older stove, proof that you have maintained it, via annual chimney sweeping will make a difference.