To ask the Deputy Prime Minister what regulations are in place to control the (a) size, (b) speed and (c) height of remote controlled planes and other leisure aircraft flown in public areas. 
I have been asked to reply.
All aircraft, including remote controlled planes and leisure aircraft are subject to regulation by the Air Navigation Order 2000.
Size is determined by weight and regulated by Article 129. This defines any unmanned aircraft, other than a balloon or kite, weighing not more than 20 kg without its fuel, as a 'small aircraft'. The speed of small aircraft is not specifically regulated but they are subject to Article 64 which states that a person shall not recklessly or negligently cause or permit an aircraft to endanger any person or property. Article 87 limits recreational model aircraft to a maximum height of 400 ft above the surface.
Remote controlled model aircraft weighing more than 20 kg are only permitted to operate in accordance with an exemption issued by the Civil Aviation Authority. They are subject to Article 23(1) of the Rules of the Air 1996 which limits an aircraft flying below 10,000 ft to 250 knots.