Another reason will never know the full total is that, in the early weeks, many of the deaths at home and in care homes - did not have CV19 on the death certificate. Pneumonia and other causes, yes. The reasons for this do not matter - it happened. THAT then affected other numbers.
More importantly, as is regularly stated, as we have not tested anough people in the uk (randomised and repeated) we have no idea of the Case Fatality Rate.
Lastly, a proportion of the excess deaths now being experienced in the UK, are due to people not attending treatment sessions, people having surgery postponed, people not wanting to go to hospital for fear of catching the virus. So these deaths are 'collateral damage' of the virus and the way the UK has responded.