ONS latest estimate was 576,300. https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/bulletins/coronaviruscovid19infectionsurveypilot/18december2020#number-of-people-in-england-who-had-covid-19
At that rate I don’t know how we all haven’t had it by now!!