Correct. The UK FIRs (London and Scottish) do not indicate or imply any sovereignty over such airspace, at least that outside territorial waters. ICAO signatories agree to provide alerting and flight information services within such airspace and nothing more. Have a look at the FIR boundary between Northern and Southern Ireland; it doesn't follow an international border so who is responsible for what if you're inside the Scottish FIR but over Ireland? Who's going to shoot you down? The answer is that there are numerous bi-lateral agreements such that cross-border civil aviation continues with safety.
Airspace designation - no country has the RIGHT to impose any form of airspace control or restriction outside of international waters. It is common practise to recognise conditions that countries have applied in airspace outside of territorial limits but no one is obliged to comply with such conditions. Someone mentioned "due regard" a little earlier and that is absolutely correct.
Get over it - this was not unsafe, there are all sorts of protocols in place to protect the commercial traveller and the only effect is inconvenience.
Now, a far more interesting subject is the political intent and implication of such irritable activity.