I suppose the two most well known care homes in the London area would be Brinsworth House in Twickenham and Denville Hall in Northwood, North London. Not sure what the residency criteria is.
Amongst the current Brinsworth residents are Richard O'Sullivan and past residents include Charlie Drake and briefly Norman Wisdom.
Of the well known names at Denville, Maurice Denham was a resident as were two of the cast of Allo' Allo' Carmen Silvera and Rose Hill.