I've been on AMRAAM trials with Sea Harriers, and it proved rather good; as for launch velocity and altitude, I would think it compares pretty well with the wonder-jobs, read the figures.
Remember which aircraft - even a GR1 - won the transatlantic race against a Phantom, and the old but true story that a fully loaded Harrier is very nearly as fast as a 'clean' one, unlike most combat jets.
With AMRAAM & helmet sighted ASRAAM, upward firing chaff & flare etc, it would be a very brave or foolish enemy pilot to approach the fleet...