Okay I realise this is a derail and a dead thread but it's going to bug me if I don't reply:
The issue with Woolwich is that it is quite segregated and experiences a huge socioeconomic and racial divide, literally divided by a single road.
Woolwich traditionally is a working class area and a black area. A few years ago developers took over waste land where the former military arsenal buildings were, and put up a very fancy, very expensive gated community (which is where I own a flat). Think private swimming pools and concierges, expensive boulangeries, etc. This gentrification created a huge divide in the area, literally divided by a single road. I doubt you have visited that part of Woolwich.
Greenwich council have done a lot to try to combat this divide, and they've put a lot of effort into making Woolwich 'proper' (the area around the station and the high street) into an enjoyable outdoor area. That's why there's a huge square with many seating areas, council-funded street art, street musicians, and the tiny little miniature fairground. Woolwich does tend to have a large older population, and also fairly high unemployment, so there are many residents who I guess don't have anything else to do except sit and socialised in the square and on the high street benches all day. Woolwich has an outdoor socialisation culture which previously I've only experienced outside the UK, and I guess you need to get used to it. People are not "creepy" just because they are unemployed or poor or because they come from an Afro-Caribbean culture where it's more commonplace to hang out and socialise outdoors.
Plus... I'm not accusing you of being racist, but I do have to wonder if the fact the people hanging out are pretty much exclusively black triggered some subconscious bias that contributed to your feeling of discomfort.