The national speed limit is 60mph, which is for all single carriageway 'A' roads not subject to a lower limit. The limit for cars on dual carriageways and motorways is 70mph. But 80 - 85mph on a speedo is likely to be a true 75 - 80mph. Though the law to specifically ban radar and laser detectors was never fully passed by Parliament, I'm not going to recommend any. Unless the detector has a range of three miles (in which case it could be beeping all the time) it is almost impossible for these devices to detect a laser trap before a skilled laser trap operator clocks the car.