I think of Research Enterprises as a wartime group set up to develop radio and radar systems in support of the war effort. One of their projects had several groups of FWD trucks modified to make radar stations (generator, equipment, operators seating etc.).
This suggests that your C60L might have been a truck used in support of one of these radar setups, either GS or a specially adapted variant.
I know some of the group here have more information than I do on Radar support vehicles, perhaps they can help.
These two websites give a little information on REL:
http://www.radiomuseum.org/dsp_herst...ompany_id=9562
http://www.lostrivers.ca/points/ResearchEnt.htm