The Wellington in the crew pictures and featured on each page on this site appears to be an aircraft from 26 Operational Training Unit (OTU). 26 OTU used the call sign EU which can be seen on the side of the aircraft in the photo below. It isn't very clear from the photo what the serial number of the aircraft is, but this appears to read DV895. Cheddington was also known as Marsworth was located near Cheddington in Buckinghamshire. Using maps from today it actually looks like the airfield was near to Long Marston and was used as a site for raves in the late 1980's. Cheddington opened in March 1942 as an OTU station and it remained in RAF use until September of that year when the US Eight Air Force moved in. 
Wally's Wellington from 26 OTU at RAF Cheddington. Wally is second from left.