JudgeJ, your answer is not necessarily correct. Before I left the UK I lived in a Cul de Sac which was built in the early 1960s. Although the pipes used for the sewage system were legal, they did not conform to the standards required by the local authority, which refused to adopt them. (we didn't know this when we bought the house - it didn't show up in the search or the deeds).
When, in the 90s, they started to leak, it was determined that all those on the "wrong" side of the leak would have to pay. However, our local councillor got involved and negotiated a deal with all the individual homeowners' insurance companies, whereby we all (even those of us on the "right" side of the leak) made claims. The entire system was replaced, and the local authority then agreed to adopt it.