There is a transport bookshop/model shop in Lower Marsh next to Cubana ( I can't think of the name) they sell the old ordnance survey maps and had some of the areas you're looking at. I guess one of the larger Southwark libraries of archives have some too, probably worth a call before you go.
I'd agree on the Mapco site. It's a wonderful resource.... and I think they should restore some of the old names. I particularly like the idea of one end of Gt. Suffolk St. being restored to Dirty Lane. :D
I picked up facsimile Ordnance Survey maps from 1894 & 1914 in WH Smith in Lewisham - they're printed by Alan Godfrey maps in Gateshead, they might be able to order them for you? Fascinating as they list all the different businesses on the back.