Driving sensibly and courteously on a motorway in good conditions it's extremely unlikely that traffic officers would show any interest if you were doing 80 mph (in England anyway - Scotland may be different). Pass a fixed speed camera though and you'd be quite likely to get an FPN (or SAC invitation). Actually most of the forces down here abandoned 'patrols' on motorways many years ago. So if you see a car it's almost certainly on its way somewhere, making it even less likely they'd want to get involved in a stop for simply doing 80. IMHO.