5th city of france as well. Yesterday was at a barbecue in Sevenoaks (small commuter town, traditionally very, very English) - the people present were...
Swedish
Polish
German
Japanese
Russian
London and the surrounding area has become a very international place (always was, but has become much more so in recent decades.
Jobseeker's allowance is meant to fund those things as well, but try taking a train from, say, Yorkshire to London for an interview at short notice - you wouldn't be able to afford the ticket.
Think free travel to interviews is something that should be looked into. Jobseekers allowance just about covers food. Though housing allowance, exemption from council tax, etc... are very generous.
I think you're right on the British being the least mobile, major limitation is that English is taught very widely abroad, but the British rarely learn any foreign languages beyond a basic level and the typical language learned is French, which isn't very useful. German, Spanish, Mandarin - those would be good.