I live in a desert, Temp. today is 110 degrees F. However the humidity is only around 15 %. It only rains about 20 days of the year. Have house on 1 1/4 acres with lots of plants/trees, and a swimming pool that evaporates about 50 gals. per day, and automatic , underground sprinkler system. My annual water bill is about the same as yours, no hosepipe ban. I agree, I think you guys are being screwed.
At that cost it probably costs 05 P. to take a dump and flush. No wonder I saw so many people walking funny when I was last back in the UK.