to answer some of the points - options with consent or EA informed is to discharge into the river - the excessive amount or unnotified discharge is what water companies get fined and prosecuted for.
there is legislation for suds so we see a large amount of suds being formed - mostly its done on a financial incentive and housebuilder can claw back some money for doing so (dont quote me on that) - foul water still need to connect to the sewer network
rainwater = waste - well due to the language and terminology used in law, the adoption of SUDs is an area that is being looked into - for the mean time i dont see why agriculture couldnt some of it or even for firefighting purposes
the strategic water plan is miles off where it should - at least 10 years in some towns and cities - there is no capacity within the existing highway infrastructure to lay new pipes so could be looking at greater distances or private land being used (all subjective)- water companies are a business and with privatisation (rightly or wrongly) means they need to make a profit/turnover (apart from welsh water which is not for profit)
also on most housing development - the concept of green infrastructure such as garden roofs etc are not done - its cheaper for mass production of a traditional pitch roof frame and bang it all on site in a day - the only SUDs I've seen looking at plans is a large ditch or two