I'm working on creating heights of polygons above terrain level, as in this blog post, but my area of interest is London Borough of Camden.
Camden is the green shaded polygon on the map below, generated using the Environment Agency's 1M resolution DTM and DSM LiDAR composites. As can be seen, coverage for Camden and neighbouring Islington is almost completely lacking.
Are there any other data sources that might be available to fill in the gaps?