In narrowing dowm the refuges, it might be helpful to divide London up into the zones that need to be covered. I agree that the East End/Limehouse/Docks must be one and that Clubland/the West End/Belgravia another, to cover Parliament/Scotland Yard/Victoria Station (although perhaps the Diogenes served this function, although not itself one of the 5). I am inclined to another in The City, especially to cover the Financial district, Courts and Inns of Court,etc. Another probably near his old haunts of the British Museum, but a bit north towards the railway stations of King's Cross, St.Pancras and Euston. And, at least one must be south of the river, possibly near the crossroads of Elephant and Castle or in the neighborhood of the Crystal Palace, if not closer to the bankside.