Sorry people to add another fly into lessening ointment but as this is a topic for everyone and not just those who fly into major airports. In the UK speed limit points may be ignored when instructed by ATC in class A-D airspace only. In class E-G airspace you are expected to be less than 250 knots below FL100 under the see and be seen principle. Whilst this may seem like a mute point dont forget that Glasgow Airport still has class E airspace around it and there are many more airports becoming busier in open FIR.