They can do as much research as they like - unless someone manages to force a change through OFCOM, mobile repeaters are illegal in the UK except when provided by the mobile operators. Broad spectrum repeaters are completely banned.
Unless one happens to be the Olympics, which is the only instance of mast and network sharing between operators I can think of in recent history.
The Vodafone Suresignals are crap, as are most of the other equivalents unless one only needs to cover a small office of half a dozen employees. You can't easily use more than one nearby, because they don't hand calls between each other, so if you walk into stronger signal range of the next unit, your active call will drop.
We also looked into the serious commercial offerings from the operators - at an average of £5000 per year per access point, and the average building floor needing 6, it gets real expensive real fast. Fine if you happen to be backed by Arab oil wealth, for the rest of us though, not so much.