We have had a smelly bathroom (wastewater smell) for several years

We have had a smelly bathroom (wastewater smell) for several years. This has been addressed by different plumbers who installed one way valves on the toilet outlet, on the vent into the roof, and various other methods. Nothing worked. Then we were advised to contact Schmidhauser who advised placing a 110mm vent pipe outside of the bathroom into open air to allow any wastewater smells to escape outside of the bathroom and roofspace and eventually, we have a solution. We found all the contractors used by Schmidhauser to be professional and well trained in their respective types of work - since the job entailed plumbers, builders, plasterers and a carpenter to remake a box to house the toilet and shower/basin pipes under a covered box. They even put a lidded covered space on the box to house extra toilet rolls or sundries since it is a small bathroom. A complex job done with really excellent workmanship. Thank you Schmidhauser.