You can download a PDF version suitable for printing here: natural_london.
I’m pretty happy with the result, my first real attempt to produce something useful with QGIS. The data I used was:
There’s no reason the Natural England data couldn’t be manually added to OpenStreetMap, giving us a complete dataset of natural features. I just chose to get on and do it this way rather than wait, or try to add all the data across areas of the city I don’t know well and am not going to visit any time soon. I also didn’t really need to use the Ordnance Survey data for boundaries, but it’s slightly more accurate and complete than OpenStreetMap data.
The map is probably missing lots of smaller patches of green space, including grass verges, green roofs and biodiverse brownfield sites. The biggest omission is the humble private garden. They cover 24% of London’s land!
But the map at least shows the more obvious, visible, public green spaces, and is a nice example of what a geek with no GIS training (but years of playing with OpenStreetMap) can do with free software and free data these days.