They have been upgrading it in bits and pieces. There was a hi-res area over London and another one to the west, around Maidenhead. Now they have inserted another one in between, covering (most of) Heathrow. Where the Heathrow and Maidenhead sectors overlap they don't quite join up, and there's one particular installation - the Dorney rowing course - which was under construction in the older image but complete in the newer one and the difference is very evident. (Looks like a 2000m runway, in a loop of the Thames).
The area where I live, on the other side of the Channel, was recently upgraded from lo-res to hi-res. You can tell these areas, they are shaded brown or grey.
You can always go searching for Concordes - I've counted three (not counting the half-size LHR gate guardian).