The police came to talk to me last night, and basically told me there's little to no chance of a resolution, and that the phone is probably already sold on or on its way to Taiwan or something. I pretty much assumed as much.
It's reported as stolen though, and I told the phone company the specific ID number of that handset, and they locked it down, which they said means that whoever has it now, it's basically a block of metal in their hand and useless to anyone. I guess that's the best I can hope for.
When I told him where it happened, he basically rolled his eyes and agreed that it's one of the worst areas in London for that. There's gangs of them roam the streets and it's all highly organised. But I have a case report number and I can get proof of purchase from the phone company, so hopefully that will be enough to claim on the home insurance, because I didn't have insurance on the phone itself.
Silver lining - the phone was so new that I hadn't actually got rid of my old phone yet. So I just transferred the number back over to the old phone, and away I go. Still pissed off, though.