FFS! the guy sounds like he's got a few bob and wants to stay somewhere decent! you're hardly going to want to stay somewhere like herne hill or stockwell or half the places folk are singing the praises of on here unless you're up against it.
i'd also say he should check out archway, highgate, chalk farm, around there. i've been around there for years. well cheap, lots of massive old houses, good tube service and night busses, can get anywhere and everywhere in london worth going to in 30 minutes from my door, lots of good old man pubs and crackin restaurants and fairly quiet unless it's st paddy's day, i've never had any stick or seen any trouble anyway and i'm out every night and stoatin back all hours.
to me what it's all about is:
1) location/accessability to everywhere by tube and bus.
2) old building, thick stone walls and large rooms, none of that new rubbish or knock through bollocks.
3) lack of nutters leaping about trying to rob folk or wallop them over the head to pass the time of day.
and as nice as you can get for as cheap as you can get