That's because your water authority is not the greedy money grabbing thieves that are South West Water. We have the highest water rates in the country; the average down here is about £520 pa compared to about £340 in the rest of the country.
Indeed, but the OP was being charged at the Rateable Value of the property, which is NOT set by the relevant water authority.
The end customer always has the option to meter the property and, in the South West, has the option to revert to RV if it is more beneficial to the customer within 12 months.
The average for a single occupier in the SW region is about 28/month, thats water, sewerage and surface water drainage.
There are lots of ways to reduce consumption as well. to give you an example, I pay under 50/month for 5 occupiers for water & sewerage (no SWD) and thats all normal everyday use.
OP . If you have any questions related to SWW charges, you are welcome to drop me an email (in trust)
I have done some work with SWW in the past.