At least in the US, this is a terrible idea, some cities have quite crowded TV bands. Other areas? Well, I live in a city, but there's only 2 local channels. The rest are 60+ miles away, some are considered to be in a different market and so would be considered "fair game" to broadcast right over as far as this junk is concerned. I'm DEEPLY concerned about this type of equipment being too lax in what it considers "white space", and being sloppy in keeping it's transmissions within it's channel.
One reason a database is being required? The companies LIED. Microsoft and Google (what odd bedfellows) were two proponents of this, initially assuring the FCC that of course they can detect TV signals and avoid broadcasting over them. MS submitted hardware, which flat-out FAILED to detect existing TV and broadcast right over it. They said the hardware was faulty (my response -- so what? If your hardware is going to fail "interfere with TV" instead of failing "don't transmit at all", it should not be certified.) They were allowed to submit again, it failed a SECOND time.
Secondly, using this for some M2M thing that may transmit kilobytes a second? What a waste, a grand total of 1mhz would be ample for the type of use they are envisioning, I'm sure they can just license it from Ofcom (since a slice that small can't be used for a cell phone network, TV, or broadband data, there's loads of little slices like that available here in the States, I can't imagine UK would be different.)
Finally, these same economies of scale that apply to this whitespace system they propose are beginning to kick in for conventional cellular equipment too, the devices AT&T and Verizon are selling for use in a house are under $100 subsidized, so a real price of under $500 (they've been calling them microcells, but I think they are actually a femtocell in the grand scheme of things since they usually only cover one flat), but microcells are dropping fast in price too. The thing is, I don't think physical equipment is even the big cost of building a network these days -- it's the labor to install it, the payments to obtain space on "towers", on top of buildings, etc., to locate the equipment and antennas, and so on.