There is no "fair" way, that's the problem.
DH and I live in a large house in Surrey. We pay a large CT bill. We pay to SurreyCC, Surrey Police, town council, parish council. Covers all services you would expect, schools, roads, police, fire, social services (for which we now pay an additional levy), refuse, and additional village amenities.
However, we are only two and pay considerably more than a smaller house down the road, with six occupants. Substantially more if done on a per person charge.
So, that's not fair either, other than we do, as wealthier, already subsidise that house down the road. So actually is this not, in fact, already fair and progressive.
Note, that a single person gets a reduction, because they are single, but a multi-occupency house does not need to pay more, regardless.
You could therefore see it as being totally progressive.