I can highly recommend Scott Leonard (plumber and business owner) and his business partner John Loveday as being the only professionals who managed to cure the sewage smell mystery in my plumbing. They did this using their imaginations, experience and professionalism. They investigated the problem thoroughly, explored the possibilities of cause, thought 'outside the box', and came up with an elegant solution.
They were polite and courteous, efficient, neat and tidy and reasonably priced.