Hi Steve
Welcome to GMIC, sorry to say you are on a hiding to nothing as most forces did not keep very good records for specials. The best I have ever seen are WWII Gloucestershire. The biggest problem is that specials medals, unless you get the box it came in do not state the force served in.
So you don't even have a starting point. Best of luck with your research, if you think they may be from Cambridgeshire I do have a few names only WWII though, unfortunatly even group photos of which there are many are not normaly named.
Alan