I have been considering this for a while, and I suspected it would be one of those "data entry on a rainy day" things to do - manually update the database so the UK Free TV mapping pages show the connections between the transmitters.
These are available for all switched-over regions, plus Oxford, minus (for some unspecified reason) the Carmel group in Wales and the Torosayand Selkirk groups in Scotland. Also missing is Stockland Hill in England.
If anyone has the Carmel, Torosay, Stockland Hill or Selkirk information, please let me know!
In addition, a separate symbol is now used to denote "Freeview Light" transmitters that only carry the public service multiplexes BBCA, D3+4 and BBCB, or will do after they have switched-over.