Ford KA engine revving on braking

sounds like you have a air leak via the vacuum system of the brakes ie servo / inlet manifold get the car to a garage to have it insoected unless you now someone in the trade that can look at it for you but it sounds to me like that or have a second person handy open the bonnet and start the car press the brake and visually see if anything is catching the cable or listen for leaks ie hissing noises

These vehicles are common for idle air control valve problems and cleaning them like on a\lot of vehicles does not work as they are electrically worn out and the only solution is to replace them, also like many of the ford range the ecu's become lazy to respond to the throttle position sensor, they usually have 0.6v with the throttle closed and are not adjustable like older cars, however i normally remove them, drill out the brass sleaves and elongate the holes so i can adjust them down to 0.5V and this cures the problem.