Historic electoral registers are often held in public libraries, local history collections and/or borough and county archives.
London Metropolitan Archives has the registers for the London County Council area.
Others can be traced through Jeremy Gibson's Electoral Registers 1832-1948; and Burgess Rolls: a Directory of Holdings in Great Britain (Bury: Family History Partnership, 2008), a copy of which is kept at the Social Sciences Reading Room Reference Enquiry Desk.