Blackcastle was a small town in Yorkshire, England. (AUDIO: Doctor Who and the Star Beast)
In 1980, Beep the Meep crashed his neutron drive star cruiser into the Blackcastle steel mills. He was later found by Blackcastle residents Sharon Davies and Fudge Higgins. The Fourth Doctor learned of the crash and travelled to Blackcastle to investigate. The town was sucked into a black hole when Beep attempted a star jump, but the effect was only temporary as the Doctor had reduced the power of the ship's engines. (COMIC: Doctor Who and the Star Beast)
The Doctor returned Sharon to Blackcastle after she had travelled with him for some time. However, she was now aged to adulthood and was uncertain she wanted to go home, but before they could leave the TARDIS, they were transported aboard Varan Tak's ship. (COMIC: The Collector)
In 1995, Beep returned to Blackcastle to retrieve his spare starship drive, but the Doctor trapped him within a Lassie film. (COMIC: Star Beast II)
During the Battle of the Game Station in 200,100, the by-now-city of Blackcastle was bombed by Daleks, and became uninhabitable, but a sizable camp was built nearby. One reporter gave the news from the outskirts of the Blackcastle's ruins. (AUDIO: The Year After I Died)
In The Year of the Pig Toby reminisces about his farewell concert in the Alhambra (theatre?) In Blackcastle.
Behind the scenes
Beep the Meep's Grundian Egg Nog recipe in Short Trips: A Christmas Treasury makes reference to the time the Most-High (Beep) "gave a Grundian Blood-Nog to more than a hundred despised human scum in Blackcastle Steel Works."