Honestly, I'm really bored of Anglo-American primary Bond girls (in terms of the characters) right now. We have had too many fellow agent/official ally Bond girls in the last decade - both Jinx and Miranda Frost in DAD, Vesper in Casino Royale, Strawberry Fields in QOS, Eve Moneypenny and M in Skyfall.
Erm, well since Vesper Lynd and Strawberry Fields were actually civil servants (in HM Treasury and the Bolivian consulate, respectively) it's no surprise they're British. Likewise, JUST LIKE JAMES BOND, it's perfectly logical that MI6 would hire British people to work for them, like Moneypenny, Miranda Frost and M (especially M).
To be honest, I'm not even sure Eva Green's Vesper is meant to be British anyway, she just works for the Treasury.
So the only character you're right to be displeased with would be Jinx, as the filmmakers actively chose to have an NSA character, and therefore an American.
But let's not forget QoS's Camille, who was ever so slightly South American. Just a smidgen. A little Bolivian. A teensy, weensy bit.
I also assume your comment extends to the male agents too, in which case Q and Tanner shouldn't be British.
The fact that ex-MI6 agent Silva is Spanish is irrelevant, I guess. And Italian Mathis definitely doesn't count.
In short, I'm quite happy with the logic behind the series' representation of ethnic minorities in the British Secret Service and cast in general, particularly in the Craig era. Long may it continue.