Magpie Electricals

Magpie Electricals was a radio and television shop located on Mafeking Terrace, Muswell Hill, London. In 1953 an alien called The Wire contacted the owner, Mr Magpie, to help her get a physical body. (DW: The Idiot's Lantern)

Although Magpie himself was killed by The Wire, Magpie Electricals survived the loss of its proprietor, and continued to exist well past the 1950s:
 * It appeared when the Doctor flicked through various websites on a mobile phone in 2007. (DW: The Runaway Bride)
 * Martha Jones had a Magpie brand television in 2008. (DW: The Sound of Drums)
 * The alien cruise liner, Titanic had a Magpie-brand microphone, though it was not known if this was a genuine Magpie device or a replica. (DW: Voyage of the Damned)
 * Wilfred Mott had a Magpie branded television, which he had when he sold newspapers on Christmas Eve 2008. (DW: Voyage of the Damned)
 * Sarah Jane Smith's computer was a Magpie Electricals brand in 2009. (SJA: The Mark of the Berserker)
 * Torchwood Three had an old Magpie television in 2009. (TWN: The Undertaker's Gift)
 * The monitor, the typewriter, the keyboard and a miscellaneous control by the mustard dispenser in the reconstructed TARDIS' console room had Magpie's Electricals brand on them. (DW: The Eleventh Hour) A power control device in the console room had Magpie's Electricals brand and was labeled Type V 310 A. (DW: Vincent and the Doctor)
 * A roadblock within Starship UK had a Magpie's Electricals banner above it in the 33rd century. (DW: The Beast Below)

Behind the scenes
The use of the Magpie Electricals logo is something of an inside joke for Doctor Who's design team. It is on the back of the monitor on the Eleventh Doctor's TARDIS. This was revealed in an episode of Doctor Who Confidential (Doctor Who Confidential: Call Me the Doctor). It was also said on the TARDIS tour on the Doctor Who BBC website.