EastEnders was originally planned to be filmed in a real square (Fasset Square) in Hackney, but this was considered impractical, so the 'lot' at Elstree was built.
There have been 3 Coronation Street 'exterior' sets - the original, which was actually built in the studio, a (quite small) exterior set used from 1969-1982, and the current set used from 1982. The 4th exterior set will come into use sometime next year (barring any further construction problems).
Additionally, there have been 3 Emmerdale/Beckindale villages - the original village was Arncliffe, then Esholt from 1976, then the current purpose-built village in the grounds of Harewood House.
The only location to have been used consistently throughout the show's 40-year history is Creskeld Hall, which doubles as the exterior for Home Farm.
The exterior set for doomed BBC soap 'Eldorado' cost ten times what it cost to built Albert Square, yet the soap only lasted a year.