With the boiler and rads cold, use the bleed on the rads to reduce the pressure, catch the water coming out, the red valve, I assume is the overpressure valve, only the plastic bit on the end would be red, turning it would reduce, pressure, BUT not recommended to do it that way, can damage some, and leave it leaking, So just empty water out of radiator, until pressure down
SD, December 2011
