The physical internet: Britain's telecom estate, as mapped
Data centres, the legacy telephone exchange and street cabinet estate, and the towers, masts, antennas and satellite earth stations that carry the wireless side — from OpenStreetMap, with the caveats that implies.
Connectivity is treated as though it were weather — everywhere, invisible, someone else's problem — right up until a site needs it. The telecom estate map shows the physical objects it actually consists of.
Compute and the copper estate
287 data centres, 2,941 telephone exchanges, 13 central offices and 1,502 street cabinets. The exchange estate is a legacy of the copper network and is being decommissioned as it is replaced, which makes it interesting for two opposite reasons: it is where fibre backhaul already terminates, and it is a large portfolio of well-connected urban buildings coming onto the market.
The wireless side
7,915 communication masts, 3,502 major communications towers, 7,103 telecom poles, 670 antennas and 275 satellite earth stations. Also 93 subsea cable routes, which is where the actual internet arrives in the country.
Where this data comes from, and what that means
All of it is OpenStreetMap, mapped by volunteers, and this is the map on which that matters most. There is no national open register of telecom infrastructure — the operators hold it and do not publish it — so volunteer mapping is the only comprehensive source that exists.
The consequence is that density here reflects mapping effort as well as reality. A sparse area may be sparsely equipped or sparsely surveyed, and the two are not distinguishable from the data. Treat it as a lower bound rather than a census, and it remains the best available picture of a genuinely unmapped estate.
Sources
OpenStreetMap via Overpass, under the Open Database Licence.