Is the pressure rising even when the boilers is off, or have you noticed that the rising only occurs during or after the boiler has been on??
If the pressure is slowly rising and not dropping off, I need to ask, have you recently topped the boiler up by using the filling loops?? If so, check that the taps are fully closed, as it's possible that there might be a trickle slowly filling your boiler up.
A quick and easy way to reduce the pressure in the boiler is to take a radiator key and drain water from one of your radiators, as if you're bleeding one of the radiators.