Doomwatch: Winter Angel, 1999. IMDb lists it as a movie, though; but it is the continuation of a 70s series of the same name.
Neil Tannahill a University lecturer is asked by the former head of Doomwatch (now very old and dying) to investigate the strange happenings at a remote nuclear facility. Dangerous nuclear waste from around the world is being transported to this location for 'storage'.. and nobody is willing to say how this waste is being stored or disposed of. A investigative reporter seeking a story see's the waste being loaded into the facility, plus an accidental spillage, and strange blue glow coming from the building. He is found and meets an untimely end by being handcuffed to his bicycle and dropped into the nearby lake - and drowned.
Neil arrives on the scene and finds that something is going very wrong - and that the facilities staff are desperate for his help. The research staff - whilst experimenting with particle physics - have created a tiny black hole - which they have contained in a magnetic field. They have also been feeding it all of the nuclear waste and other unwanted chemicals as the perfect clean solution, because nothing comes out of a black hole.
Obviously, the black hole malfunctions, and Bad Things™ happen.
Found with the Google query
british series black hole waste disposal site:imdb.com/title.