West Coast
In the UK there is a speed limit of 250knots below 10,000 when outside Controlled Airspace ; neither the pilot nor ATC have authority to lift or vary the restriction........military aircraft are exempt. In the last decade there has been a huge increase in the use of regional airports, and in the UK all the Controlled and regulated airspace is based around the major airport hubs of a quarter of a century ago. This leaves many airports [that have become quite busy] with little or no protected airspace and no linking structure into a less than ideal controlled airspace system. That is why in the UK a heavy can be restricted to 250 knots....it's not ATC, it's the regulations that are the problem.