My apologies for the error, Lilian or OH - the information my architect, local Building Inspector, SEPA, Scottish Water, and DEFRA all gave me when I built my house in 2005 was that it was totally illegal - however I have found this information today on Yahoo -
"Consent to Discharge
If there’s a watercourse nearby you may be able to discharge treated effluent, but you must first obtain a Consent to Discharge. In England and Wales this is granted by the Environment Agency (0870 850 6506) — the application charge is £124. In Northern Ireland, through the Department of Agriculture and Rural Development’s Rivers Agency (riversagencyni.gov.uk), the application charge is £110. In Scotland the online fee is £76 with the Scottish Environment Protection Agency (sepa.org.uk). "
This may be an out of date site however so the prices may have gone up.