Analysis of the 2021 census by the Official of National Statistics assigned social grade C2DE to 43.9% of adults in households - 20.6 million people.
A BBC press release may have given us an insight into what tv commissioners currently deem success. Senior publicist Chris McCluskey notes that The Traitors Series 4 Episode 1 has become the most watched episode of the civilian series to date, with 13.3m viewers across 28 days - and "A third of the audience were from C2DE socio economic backgrounds (4.3m)".
The same release notes that The Night Manager drew 8.7m in 28 days for episode one of the second series, and "It achieved 2.6m viewers from C2DE socio economic backgrounds.". That's a nudge off 30% of the total audience.