Short answers, pulled from the story.
Film production started at Elstree Studios in 1914 when Neptune Film Company opened its first studios. This early venture established a foothold for cinema in Hertfordshire before World War I halted operations in 1917.
The BBC purchased the Elstree site in 1984 specifically to produce its new soap opera EastEnders which first aired on the 19th of February 1985. Many other programmes followed including Top Of The Pops, Allo Allo, You Rang My Lord, Grange Hill, Hangar 17 and Holby City.
Thorn Electrical Industries merged with EMI in 1979 renaming the site Thorn-EMI Elstree Studios after their CT scanner invention debacle caused financial problems for EMI. Significant job cuts occurred but survival was secured when Star Wars production began using the studios in 1977.
Imperial Studios fire destroyed three stages of British and Dominions Film Corporation on the 10th of February 1936 costing $2,250,000 according to Calgary Daily Herald reports. Alexander Korda made one of his greatest successes there with The Private Life Of Henry VIII starring Charles Laughton before the blaze.
A Save Our Studios campaign led by local historian Paul Welsh MBE saw Hertsmere Borough Council purchase the remaining site in February 1996 for two million pounds. They invested ten million pounds in renovations plus construction of two brand new stages.