I've stayed at Abbey Wood a few times recently due to having a family member in hospital in London. It is lovely site and the location is great for visiting London. The train station is less than a 10 minute walk away and trains into the centre of London are very frequent. There's also a large Sainsburys at the other side of the train station and a few convenience shops in the village centre. If you were coming for reasons other than hospital visiting, it is also close the Greenwich and I'm sure you could have a great time in the city and then retreat to the relative peace of the site.