One of the UK's largest and most unfortunately named phone sellers, Carphone Warehouse, is apparently fully stocked with the still unannounced Nexus 5. The leaked screen shows 1500 units of the white Nexus 5 in stock, but there are allegedly 1500 black units as well.
The screen does appear to be from the Carphone Warehouse system, which uses a distinctly archaic blue-yellow interface. You can see the same UI in last year's Nexus 4 leaks. The search above shows 1500 white Nexus 5s residing in the Wednesbury warehouse, which is a real Carphone location.
It's not clear if this is the entirety of Carphone Warehouse's launch stock, or if there will be more arriving prior to the big day. Of course, we don't yet know when that will be.