I photographed these M3 Grant Medium Tank at Dubois and the IWM Duxford.
The M3 Grant and M3 Lee are essentially the same (the Grant was modified for British requirements in North Africa). The primary difference is that the Grant features a lower-profile, redesigned turret (for a 37mm gun) that accommodates the radio and has no top cupola, whereas the Lee has a taller, boxier turret with a 37mm gun and an additional machine gun turret on top.
The M31 Recovery Vehicle was based on the same M3 chassis.