Just because you don't see any usage in your area (rural/suburbs?) doesn't mean it's unused. They could be heavily used major metropolitan centers, for instance.
This is absolutely true. Some devices only transmit occasionally. Not everyone is blasting their frequency 24/7.
It reminds me of when I worked for a company that had a bunch of super-cool switch 56 linking various radio stations in our network. We'd use them for moving audio around, doing interviews, sports remotes, etc...
But we also had a problem with them constantly failing. I was told by our engineer that this was because whenever another company called up Bell Atlantic to get one installed, some tech would listen in to the pairs (presumably with a scope), and when he found one that was silent, that was the one he used for the new company. Often, it was one of ours, so when we would try to use the link the next morning, it wouldn't work.
It still "belonged" to us, but because we weren't using it 24/7, someone thought it should be reallocated. Not cool.
That said, I’d like to see more allocation of spectrum for consumer use. It’s very frustrating that cellular companies get more and more spectrum but we can’t feasibly deploy public LTE for example.
Perhaps if the wireless device has GPS and network connectivity we could give the government permission to enable and disable extra frequencies depending on location. Though of course this scheme invites suppression of dissent.
I can go and get prime operator spectrum if it isn't in use in my local area, and use it at certain agreed power levels. That license is just for one location.
There's also dedicated "held back for sharing" spectrum in the N77 5G band (3.8 to 4.2 GHz), which is more widely usable without detailed coordination (but you still need a low cost license)
With modern spectrum access systems (see CBRS for example), geolocation of the radio is used to determine via a coordination server what spectrum can be used in a given location. Whether that's at risk of suppressing dissent or not is another discussion however - most radios in cellular networks will have some kind of backhaul and coordination management plane for interference avoidance and management - the threat model in cellular technology is a bit different still, and the communications are there to enable spectrum requests to be made in real-time. Spectrum coordination wouldn't need to be done by government - there's conceivable ways to do sensing and avoidance, but at the risk of tragedy of the commons scenarios.
They used to have a number of spectrum monitoring stations, however they were decommissioned, I know someone that bought bits of it at auction.
A lot of the new "shared" access licenses do not give guarantees of interference protection though, so I imagine Ofcom enforcement would be on a best-effort basis there.
With some of the work coming through the pipelines though, in future it will be feasible to deploy your own small cell, either independent of an existing operator, or in partnership with a co-op or other facilitator who provides the mobile core capabilities, and run a mini network in your local area. This is already happening in the UK in various commercial trial projects.