That's not normal for us but we don't have any grass - however, we do have trees.
Our bills have been 400 in the winter and 1400 for last month (June)
If you search on here for DEWA JVT other people have had problems with leaks and huge garden watering bills so when I moved in I was super paranoid. As a result I have written the metre readings down every month and kept a spreadsheet (am v proud of myself as I'm not normally that organised!)
I don't suppose you know the metre readings from the beginning of the month?