Presumably a modern British sub or 2 armed with spearfish is more than capable of keeping the Argie navy pinned into its own waters??
Arguably, in the current climate, our best response to similar hostilities now would be to do the same thing, albeit with a suitable warning of intent, something along the lines of 'we don't have the time or resources to fight on your terms, these are ours - we will sink everything that crosses the line. You have been warned and if you don't like it, take your whinging to the UN and don't threaten military action'.
Don't know if we have the capability to do this, but like to think we do.