Vaguely relevant for those discussing soakaways and suchlike is your water charges. Our bill, and I'm sure most, is split into a supply bit and sewerage bit. I've lived here 25 years and only last year realised that the 'output' charge included groundwater. All my gutters etc. go to soakaways. I filled in a detailed* but simple online form and my charges are now reduced by about £40 a year. Not massive but worth asking for. What's more, the rules allow you to back-claim for up to 6 past years if you have occupied the property that long. I now have a £240 credit sitting on my water account (they would have sent me the ££ but I will just run it off against my 6 monthly bill). It might not be the same in all regions but worth a look.
* the rules say ALL groundwater must go elsewhere from the drains, so they ask things like do you have a patio or hard driveway, where does that drain, do you have water butts, where do they overflow to etc. Thorough but clear and fair. They reserve the right to come and have a look but in my case didn't.