The Agents chose the meeting site for being an area left undeveloped owing to recession, and for having low real-estate value. The latter is in part due to its isolation from police, as well as the presence of gangs who've shot at each other before. (The myths that the U.K. has no thugs with guns in 2009, and puts land at such a premium that there are no "industrial wastelands" like in the U.S., is easy to dispel with a 30-second Google search.)

And the PCs know that the gangsters know that West is a maverick, acting without departmental sanction. The leading theory is that the mob's boss has an infiltrator inside MI5, probably dating back to the KGB days. It's possible that these thugs were sent when this mole tipped off their boss that West had gone to an isolated meeting without backup . . .