The first place to look for answers to questions like this is the Six Bells Junction website. It is not comprehensive, but has good coverage of railtours promoted by the major operators.
This gives the Waterloo departure time as 0959 see here:
As this was a Railway Correspondence and Travel Society (RCTS) trip then their magazine
Railway Observer is also an obvious source. The 30/04/66 train was a repeat of 16/04/66 and both trains are covered in a single report in the July 1966 issue.
The
Railway Observer report has a lot of detail but it does not give timings. It mentions that the empty stock on 30/04/66 was brought in by 35030 but there's no suggestion that it provided rear end assistance on departure in either the Six Bells Junction or
Railway Observer reports.
The RCTS may have more information in their archive.