I have just one personal memory. I can't recall the year but it would have been 1972 - 1977 very latest but most likely earlier so around age 10.
This was a Cotswold Line Merrymaker to Blackpool South for the illuminations. I wonder if South was stated on the flyer or just Blackpool so arrival / departure was expected to be at North. Rather than the expected loco, normally a 47, and stock it was a collection of DMU's. I don't know if it started back at Oxford or only perhaps Moreton-in-Marsh. Bromsgrove was a pick-up. The coaches were not labelled which by Bromsgrove was a problem. On the return the labels had been stuck up.
The combined set made it up and back, 350+ miles excluding ecs, but not a pleasant experience compared to the normal MK1 or occasionally early MK2 stock. I can't recall if any catering provision as normal on a Merrymaker but we had coffee's etc on the seafront before going to the train. Would South then have had left luggage lockers? On Merrymakers we often left a bag of food & flasks but for Blackpool may not have done. When did left luggage lockers get removed due to the activities of the IRA ?
In the early 1970s there was a timetabled Summer SO return train between Birmingham New St and Blackpool North which was booked for a DMU.
During the height of summer (June to early September) this train returned from Blackpool at a very conventional 14:30.
But unlike most Summer SO extras (which ran out of steam late August or early September), this train continued to run through the Blackpool Illuminations season. From mid-September to the end of October, departure of the return train from Blackpool was much later, at 23:00.
While Brum had plenty of DMUs going to the seaside on Saturdays, and 121 miles each way to Blackpool was not the longest, this late-night return trip always sounded to me like one of the most miserable - in a weary, "had-enough-and-just-want-to-get-home" kind of way.
It was booked for a low-density DMU unit as opposed to one of Tyseley's non-gangwayed suburban fleet (but not to say a high-density set wouldn't appear if necessary). Even so, I can't imagine a much worse end to a day out than sitting for 3¾ hours in the early hours of the morning in a 1st Gen DMU, alternating between the vibration & rattle at full throttle down the WCML, and waiting in the dark at some random location to get past a Saturday night possession for WCML electrification work. Especially if Blackpool's October weather had been unkind and you were already cold and wet, as well as tired and half drunk.
To top off the whole experience, you would be deposited in the delightful environment of Birmingham New Street at 02:45 on a Sunday morning, with the prospect of a Night Bus for the last leg home.