There is a beautiful method of achieving this, explained at great length by badgerrhax in the excellent video here:
https://invidious.snopyta.org/…ality=dash&dark_mode=true
[Blockierte Grafik: https://ipfs.io/ipfs/QmewxA7nraJAyKC7eUTwmcVWRkoaifh1M43TsyEBwbfT9b]
It is a lengthy and painstaking process, but it is lovely to see the Ordinance Survey imagery onto TF2 terrain. However, if you want a larger map, or have a map with a coast, there are difficulties about getting sea level right.
I hope that Urban Games could thank badgerrhax for donating such high technical knowledge to the game. I also hope that this complex process could be largely automated for us by the use of an in-game tool.
(I am surprised there are so many bots in the poll. Perhaps they arrive by steam-engine...)