plumbers London About 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
Wikipedia about the history of the plumbers
Quick look in to the history of the plumbers, thanks to Wikipedia:
The word "plumber" dates from the Roman Empire. The Latin for lead is plumbum. Roman roofs used lead in conduits and drain pipes and some were also covered with lead, lead was also used for piping and for making baths. In medieval times anyone who worked with lead was referred to as a plumber as can be seen from an extract of workmen fixing a roof in Westminster Palace and were referred to as plumbers "To Gilbert de Westminster, plumber, working about the roof of the pantry of the little hall, covering it with lead, and about various defects in the roof of the little hall". Thus a person with expertise in working with lead was first known as a Plumbarius which was later shortened to plumber.
Źródło: https://en.wikipedia.org/wiki/Plumber
Managing a broken boiler
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.