So i contacted the installer. He reckoned there might have been a power cut which might have caused it to revert to factory settings - not sure about that theory but anyway what does it matter .....
I reckon with the high humidity outside + having alot of windows open , the humidity sensor was getting confused and constantly setting off the boost to try and reduce the humidity . He sent me a video on how to reset the system
So I just reset the system and simply turned off the boost for now The system is working away fine again.
Maybe I could have simply turned off the system till Autumn but i decided to leave it on . Will prob put boost back on round Sept . When do people who turn off their MHVR systems for the summer turn them back on ? Thanks