Does anyone know any file references for this unit at the NA at Kew?

The on-line catalogue is at
http://www.nationalarchives.gov.uk/c...search.asp?j=1 and a search for...

Word or phrase = small scale raiding force

...comes up with three hits, one in the ADM series, and two in the DEFE series. These should give you something to start with:

ADM Records of the Admiralty, Naval Forces, Royal Marines, Coastguard, and related bodies
Division within ADM Records of the Navy Board and the Board of Admiralty
ADM 116 Admiralty: Record Office: Cases
Subseries within ADM 116: COMBINED OPERATIONS (47)
ADM 116/5112 Review of policy concerning operations of small scale aiding force and establishment of Special Boat Unit 1942-1944

DEFE Records of the Ministry of Defence
Division within DEFE Military Operations Records
DEFE 2 Combined Operations Headquarters, and Ministry of Defence, combined Operations Headquarters later Amphibious Warfare Headquarters: Records
Subseries within DEFE 2: MISCELLANEOUS PAPERS
DEFE 2/1093 Small scale raiding force: policy, formation, responsibility etc 1943-1945
DEFE 2/957 Small scale raiding force: procedures, responsibility etc 1942-1944

Forrest