Grantham/Gransden
RAF Grantham-Vincent House 5 Gp HQ. RAF Gransden Lodge by 1944 was home to 2 Mosquito Squadrons of the LNSF (Light Night Striking Force ie the Mossie being a light bomber ) Quoting from Michael JF Bowyer's Action Stations Revisited, Crecy Publications 2001.
The entymology suggests Grantham modification may therefore be the right one!