I thought we were in for a juicy story there for a sec.
Sorry to let you down!

You clearly don't know me too well! Even if there had been something 'juicy' (orange or apple? Or perhaps mango?

) was to be told, and a breach of ethics was somehow had, the story would be of only one nature. It would be worthy of a short novel, much akin to my average trip report
What I *can* tell you though is that getting changed in the small lavatory of an XC HST, with a very basic wash, on the way out of Dundee after arriving on the Cally Insomnie, well it's as fun and easy as it sounds. Good gravy that experience was way back in summer 2011, now a little over 11 years ago!
I can also tell you that the larger lavatory on an ex-Central Trains 158 on the 0150 Fishguard Harbour to Swansea featured a change of clothes, I must have not wanted to connect onto a FGW HST in my Pizza Hut uniform

Now that is going back a fair few years, that would have been 2005! 17 years ago, excuse me I must go for a trip down Nostalgia Avenue!
The closest to 'juicy' you'll get from me is the most recent change of clothes on a train. That was on a GTi HST from Highbridge & Burnham to Newport, after the non-forecast heavy rain in Somerset. I'd been in an athletic t-shirt, bib cycling shorts, cycling socks and my running trainers. The heavy rain was seriously unwelcome for both me and my Blue Beauty (my road bike), and I had to buy new clothes in Asda Highbridge. I couldn't afford, nor had room in my backpack, for new underwear, and imagine the fun of wearing accidentally-bought wrong-size jeans in that situation later on when I had a short ride in Wales!