Glow Worm Compact 75p pressure build up?

When i turn on my central heating after about 15/20 mins when the system and radiators are hot the pressure gauge starts to rise.After a short time the pressure relief valve goes off,boiler shuts down and locks out.I then have to wait until it cools down,it seems to get very very hot.I,m thinking it,s a pressure vessel problem but not certain.Can the pressure vessel on this model be recharged if so to what pressure and how or do i need to replace it?