Slightly high pressure in C24 Heatline Boiler. The pressure in our boiler is slightly high (should

Question

The pressure in our boiler is slightly high (should be 1-1.5 and it is around 2-2.5) - it is only 2 years old and we have had someone in to look at it recently as the thermostat was not behaving correctly - so I am confident there is not anything wrong with it - but now that we are starting to use the heat again, the pressure rises up into the 'red' area (3-4) when the heat is turned on. Is this something to be worried about? And is there anything that we can do to release the pressure?Thanks for any assistance!