Cheap: a no-frills, but very conveniently located (Fitzrovia, so a hub of sorts to King's Cross, Regents Park, Marylebone, Soho, Covent Garden, etc.) and v. near the Warren Street tube entrance. Building and rooms are utilitarian 1950's brutalism. Showers are shared. Would make a find movie shooting location for A) Cold War era Soviet Russia; B) Penal institution in Northern New York circa 1949; B) Psychiatric hospital where one has little chance of escaping without outside help; D) all the above.
Everything works, but nothing is pretty. Hallways are lighted similarly: white industrial LEDs for those that love relaxing in the machine shop. Spaces are a bit confined / narrow (not sure its ADA compliant; I wouldn't want to be in wheelchair navigating the hallways or elevators). However, very safe (but the individual floors with their bad lighting and concrete and tiled echos are a bit creepy). Pretty good breakfast on the roof with access to an outside terrace. Nice, helpful staff. BTW, did I mention it is: cheap and accessible to nearby neighborhoods?