How far from Waterloo would you go? Are you looking for ex local authority or privately built? There always seems to be stuff going in Metro Central Heights at E&C. Have you been to Edwards on the Blackfriars Road who sell quite a lot in the area (they don't publicize themselves very well)? I bought through Field and Son on Borough High St and have just sold through Winkworth in Kennington and they were both very pleasant to deal with and not just interested in luxury flats (unusual in Estate Agents).
Have you tried leafleting if you have a particular estate/block you're after? Alternatively get in touch with the residents/tenants association as they might be able to spread the word around. If it's council owned you can talk to Southwark Council to get the numbers. Good luck..it took us months too but we got there in the end.
Edwards seem to sell the most to the east of Waterloo whereas Halifax property services sell quite a bit to the west. I just saw three properties for sale on Lower Marsh the other day, there was no name on them but there were phone numbers. Edwards for some reason don't keep a list.
Some of the estates to the west of Waterloo towards Kennington are nice. The William Blake Estate of Hercules Road is Corp of London and well maintained with a lot of right to buy. The Briant next door is Lambeth, so grottier but smallish. The Wellington Mills Estate (I think thats the name) behind Kennington police station is really nice and mainly elderly people.
Behind Parliament View on Lambeth Bridge roundabout is the Whitgift which is very central, and three small blocks around a pretty park. China Walk off Lambeth Road is also OK as is Lambeth Towers. The Ethelreds is vast and bits have problems (the preferred solution seems to be to pull a lot of the red brick bits down), but there are some newer maisonettes around Juxon Street which do go for less than £200,000. And some Lambeth Walk properties are OK. You can also find purpose built private in streets like Gilbert Rd and Reedworth St off Kennington Rd which are nice and much favoured by MPs.
Lower Marsh is still the nearest shopping centre, but being nearer Kennington has advantages. More green space, plus Victoria and Battersea are then pretty accessible. Plus Vauxhall and Albert Embankment are undergoing huge changes which are certain to impact on the area pretty quickly.
Estate Agents. Alan Fraser handles a lot of ex local authority and is helpful. Halifax by Lambeth North also get quite a lot and Field and Field (think thats the name) have recently opened in Kennington Road.