As the charge is against the person benefitting from the service, could the tenant demand that he be invoiced for the sewerage charge separately, and not have it included in his rent? Thereby giving them the option to pay or not to pay?
Roger Mexico's comment on garages is also interesting, some may be liable some won't. How will they know, bound to be people get away without paying. Also what about an old boarding house converted to flats, with one connection but say 3 separate flats all paying £50 v an old boarding house rated as one property with multiple occupants in bedsits paying just 1 x £50. Fair system or what?
At the end of the day we are told it is only £50, less than £1 per week, and the electricity has only gone up by £20 or so, and the water rates a mere 3%... etc etc etc, which all adds up don't it!