The 1988 Quail map for the Eastern Region shows "Crofton Permanent Way Depot" with a similar number of sidings to the present DMU depot. It appears to have been a regular BR location rather than a private contractor.
Apparently it closed in 1994.
The place seems a bit camera shy, but I found these BR blue beauties on flickr:
03047 at Crofton in 1976, with stacks of concrete track panels behind:
https://www.flickr.com/photos/andy_hoare/5148971737/
40115 in the headshunt in 1977, waiting departure with concrete track panels:
https://www.flickr.com/photos/tunnel_one/7581558166/
45068 departs Crofton onto the main line in 1982 with an engineers train:
https://www.flickr.com/photos/blue-diesels/53656503017/
08776 at Crofton in 1990:
https://www.flickr.com/photos/dwbphotos/51550947643/
This 1955 map gives an interesting view of the area before the depot was built:
https://maps.nls.uk/view/91789063
There were two nearby collieries,
Walton (originally Sharlston West) is adjacent to "Ings Farm" on that map. Sharlston Colliery (originally New Sharlston) was nearby, on the line to Pontefract Monkhill - the connection into the colliery can just be seen at the top of the 1955 map (near the number 39). "Sharlston Colliery Pit wheel" is visible on google maps on the site of the colliery.
Also on the 1955 map, a triangle can be seen (with a sewage works marked in the middle) of which only one side survives. The trackbeds can also be clearly made out on google maps imagery. At Crofton West Junction there were actually two junctions very close together, one of which formed part of the triangle which led to Crofton South Junction and the start of the Dearne Valley railway towards Doncaster. "Crofton Hall Sidings" were located beyond Crofton South junction, and are also visible on the 1955 map. A google image search for "Crofton Hall Sidings" brings up an interesting picture of a 40 and the double junctions at Crofton West which was posted to Facebook.
Railway Memories No.6 by Stephen Chapman quotes a former driver saying "
All the coal off the Dearne Valley used to go into Crofton and we took it on to Lancashire." So there was a (modestly sized) yard at Crofton, but not where the permanent way depot was built...