With the heating off, I bleed and pressurize the system and leave for 24 hours and there is no drop in pressure, When I switch the heating on all the rads heat up the pressure gauge rises over 2bar, Leave on for a couple of hours then switch off, check pressure in the morning no pressure,
Its doing my head in
You have a leak, but only when the system is hot and at full pressure you lose water. When it cools down again the pressure has dropped. You will have to look for the leak when the system is hot and at 2bar pressure. Either that pressurize the system to over 2bar and check then. But you still might need the heat to expand the leaking part.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.