An asset search for a private individual (rather than a company) seems to be £56. If you want to know what is around your house this would tell you the route and size of sewers but I don't think they highlight the age or type of the sewer itself. The one at the bottom of the pit in Perry vale is the brick built egg shaped pattern - seemed to be quite small - maybe 18" high. The sheet piling now prevents a view of it.