All refurbishments for the Class were done at Swindon Works.
Set L430 (51368 + 59520 + 51410) apparently underwent a test refurbishment in April 1975. It was given blue linoleum, cream formica panels and blue seat coverings, but not fluorescent lights. It also retained it's plain blue livery at that time.
The 'production' refurbishment got underway in January 1977 and included all vehicles except 51368 withdrawn in 1968, Class 116 DMBS 50083 was running in its place in set L440 would be refurbished alongside the two Class 117 vehicles. When sets L433-5 were refurbished they included the three Class 118 centre cars running in them.
Until late June 1979 the "refurbished livery" of white/blue stripe was applied, the remainder were turned out in blue and grey.
The last full set to be treated was the prototype set L430 in July 1980. The last vehicles done were two centre cars (59490 and 59509) in early 1981, they were running in Class 118 sets but would soon be returned to Class 117 formations.
British Rail recorded the "production" refurbishment in an internal photograph album (and according to the cover was also intended to show the work that would be done on the 118s). The images are of set L410 which was vehicles 51345, 59497 and 51387 refurbished in June 1977.
The table below shows the Works date and the livery applied for each vehicle. Information supplied by Eddie Knorn, extracted from the BR vehicle record cards.
Summary
Orders
Description
Gangways
Diagrams
Works Photographs
Numbering & Driving Inst.
Set Numbers
Liveries
Operations
Refurbishment
Non-Passenger Use
Images
Details about preserved Class 117s can be found here.