This train and the corresponding return service must have had more route changes than any other. The PSUL (Passenger Services over Unusual Lines) website includes many of the details in its year by year listing from 1963.
In the late 1950s and early 1960s they used much of the old Great Central route (inc running powers over the L&Y between Bradford & Penistone), ie. Halifax, Huddersfield, Penistone, Sheffield Vic, Woodford Halse to Banbury.
In 1963, a portion from Leeds was added (presumably at Huddersfield) to compensate for the loss of the Midland line Bradford FS - Bournemouth West services via the S&D after 1962.
1964 was the last year for the remaining holiday trains using the Great Central and in 1965 this pair of trains was re-routed south of Penistone via Barnsley, Sheffield Mid, Mkt Harborough, Northampton, Bletchley to Oxford. Although PSUL does not show the pair going this way in 1966, I have seen a photo of one on this line in July of that year. Instead PSUL shows the 1966 pair going via the MML then Hendon Goods Flyover, Acton Wells, Addlestone Jn and this is clearly the way they went from 1967 for a few years.
For the 1970 season, the route between Barnsley & Huddersfield was changed to via Crigglestone. This meant reversal at Huddersfield.
In 1972, the southern terminus was extended to Weymouth and the northbound train was re-routed via Reading West, Birmingham and, presumably for pathing reasons, the Lifford curve / St Andrews Jn / Landor St Jn loop. The southbound train was still booked to go via Hendon.
In 1973, the southbound train was re-routed to go the same way as the 1972 northbound, inc the Lifford curve. However the northbound was not booked via Lifford so presumably reversed in New St.
There were several more route variations up to the end of the 1982 season, which can be found on the PSUL website, when the northbound train ceased to run via Huddersfield & Halifax (there was a 1983 train but it ran via Leeds). 1986 was the last year that the south bound train ran.