Try drain unblocker first it’s only a few quid from your local hardware store, if the blockage still persists you will need to give the pipes a good clean as well as the trap. Depending on how far the blockage is and ease of access expect to pay anything from £40, if the problem is due to lack of fall then it will be considerably more.
Projects that add value to your home - Phil Spencer
Looking to extend your home but don't know where to start? Property expert and Rated People ambassador, Phil Spencer, shares some thoughts on why loft conversions are such a popular way to create more living space and add value to your home.