The White part of GWS was JD Whites from Middlesbrough their yard is still there at Thornaby on Tees which was next door to where Sadlers Transport were based. Friend of mine’s brother worked for Whites, he drove at the time( 80,s ) their biggest crane ,i think i have an article somewhere about a lift they did on the Post Office Tower in London , will try and dig it out. Have posted this picture before i think, this was based at Thornaby and was taken at Redpath Offshore yard at Port Clarence, Middlesbrough about 1992.
As has been said Sparrows are a big company, they also operate and maintain the vast majority of cranes on the oil platforms in the North Sea.