I have to pay about £50 per 6 months for my water bill but 90% of that is standing charges
That’ll be for the cost of getting the water to your house, taking your poo away (depending on which one it is) and taking away the rain that falls on your house and land. All that infrastructure needs maintaining and there’s an awful lot of it.
The good news is you may be able to talk to your water company, depending on which one it is, to let them know you don’t want them to take away rainwater, you’ll do it from now on thanks. You’ll save a fortune!
Good luck, and keep their phone number handy, once you realise just how much water they do take away for you, you’ll probably change your mind quite quickly.