I live in Ipswich and can confirm the exact location of Martlesham Heath airfield for you.
You currently have your mark slightly to the East of the field itself. The light greyish and slightly darker brownish areas mark the main area of the airfield. (The last remaining hanger is in the lighter greyish complex)
The last trace of Runway (the american extension from when they took over the field in 1943) is the end of the north/south runway, with the taxiway bending off to the left of the end of the runway itself at the point:
53:03:14 N 1:15:39 E
Hope this helps.
PS. Considered a similar file for all the US bomber and fighter escort fields?