plumbers London Plumber's snake
A plumber's snake is a slender, flexible auger used to dislodge clogs in plumbing. The plumber's snake is often reserved for difficult clogs that cannot be loosened with a plunger. It is also sometimes called a toilet jack or electric eel.
Plumber's snakes have a coiled (helix-shaped) metal wire with a broader gap between the coils at the terminal end. The operator turns a crank to rotate the helix as it moves through the pipe.
If the clog is caused by a dense, but shreddable obstacle, such as tree roots or glass wool, the auger might break it up enough to enable flow. A small, lightweight obstruction might be snagged or corkscrewed by the auger, enabling the operator to pull it away. As the auger rotates, it also flails against the interior walls of the pipe, scraping off minerals and oil.
Źródło: https://en.wikipedia.org/wiki/Plumber%27s_snake
Plumbing - simple definition
Plumbing (which comes from the Latin word plumbum, which means lead, as pipes were once made from lead) is the job of working with pipes, tubing and plumbing fixtures for drinking water systems and getting rid of waste. A plumber is someone who fixes or puts in piping systems, plumbing fixtures and equipment such as water heaters. Many plumbers are construction workers. The plumbing industry is an important part of every developed economy because people need clean water and safe ways to move and store waste.
Plumbing also refers to a system of pipes and fixtures put in a building to move water and the get rid of waste that is in water. Plumbing is different from water and sewage systems because plumbing system serves one building, while water and sewage systems serve a group of buildings or a city.
Źródło: https://simple.wikipedia.org/wiki/Plumbing
Boiler repair - call in the specialist
There are repair jobs, that almost anyone can do themself, but broken boiler isn't one of them. Boiling hot water and immense pressure - those are the things that define boiler, and also the things you should be wary of.
Calling in professional plumber isn't any shame in this case, it is necessesity. It is different from a ticking bomb, but close enough, especially if the safety valves are at fault. All in all, you need expert on this - let him do his job, and relax. He is aware of the risks involved and already knows how to avoid any mistakes. All you need to do is coffee and maybe some snacks, while he do his job.
If you are not convinced by this, and ready to repair you boiler alone, all i have to add is this: search the internet for movies of exploding boilers, I dare you.