It's a shame Eurocar aren't in Lewisham anymore, the nearest is Bermondsey.
I've found them a bit cheaper than Enterprise but both offer a decent service.
https://www.europcar.co.uk/en-gb
For shorter journeys, Zipcar is ok. Especially the Flex option if you just need to go one way. Tad pricey but works out well if splitting the cost between a few people.