I did a case a few years ago where a house had not been built in compliance with the planning permission, there was no Architects Opinion on compliance and the house and septic tank had been wrongly positioned. My client had to apply for retention and the Local Authority imposed the current, more stringent, septic tank regulations.
So, yes, I think these issues will arise on redevelopment and any potential purchasers should see their architect/engineer for advice before purchasing.
mf