Erikm has it right. At about 8 tons, 6x6 and Ex British, it'd have to be a Saracen APC. They're inexpensive for their size and still able to take some punishment. I have the smaller cousin, the Daimler Ferret. Still quite capabable.
As for ballistic protection, it'll depend on the Mark, the Mark 6's had 7.62mm AP protection from the sides (all around) and were the final form of vehicle used to deal with the IRA in Northern Ireland.
No doubt, unless the knuckle-heads crossing the border are toting around RPGs or an M2 50, they're going to be dealing with more than they can handle. The Saracen will take a 7.62mm MG in the turret and one more on the rear skate ring. 8 Dismounts will help too.
The Saracen's debut was in Malaysia during the communist insurrection down there that the British won.