Baxi Combi 105 HE Pressure Gauge Fault? Continued ?

Hi b, thanks for your response 'when you say the filling loop letting by' i have checked both taps and both are turned off (cold water inlet/heating return), could there be a fault with the cold water inlet? and if so, is this something that i'm going to have to get an engineer to come out and fix? Thanks Bekki :o)