On the day I went back to Slough or got off there and didn't go to Windsor (I really can't remember). However the three pictures I took are at Slough, and can be seen here:
https://www.flickr.com/photos/rayh/shares/6m1w48. Did you go to Slough? If you did I'm sure your spotting books would contain the Hymek and Western, and maybe the bubble car too. I can corroborate your information because I still have my Ian Allan book of BR motive power which I used to underline the loco's I'd seen, and mark whether I'd been hauled and whether I had taken a photo. All the locos you mentioned were marked as 'hauled by'. I also took a picture of 5218 and 7524 but threw it away as it was rubbish. I am certain you and I were on the same trip.
I have photos from other Mystery trips in 1973 to Ayr (Sun 01Jul), Skegness (Sun 05Aug), Worcester (Sun 26Aug). I wonder if you were on any of those. I have not yet uploaded the photos to Flickr, but when I have I will post a link on this thread if you (or anyone else) are interested.
It is one of my regrets that my spotting books were lost. I would love to be in the position you are in being able to re-live the day. Fortunately my index of slides survived, along with many of the tickets I used plus the Ian Allan locospotters books. I have been able to use all of these sources to add meaningful captions and tags to my photos.
It sounds s though you were from Huddersfield so you would have missed the 'Halifax' experience at the end of most of the Mystery and Merrymaker trips that ran from there. As most of the rakes were 12 or 13 coaches they were 'banked' up the steep gradient from Greetland Jct to Dryclough Jct. The banker was usually a Healey Mills EE Type 3 and there was a cacaphony of horns before the noisy ascent. A great way to end a fantastic day out on the railway.
Thank you for sharing the information you gathered more than 45 years ago.