Way back in around 1983 there was a dispute between management and (paid) staff on the Ffestiniog Railway over pay. Not sure whether there was a trade union involvement.
The reason I remember this is that (believe it or not, it's true) I wrote a parody song on the theme for a radio programme on BBC Radio Cymru.
My recollection is that the increase offered was 2% and that the manager was named Pollock (or similar), simply because they featured in the lyrics!
As best I can remember it was something like:
Rhyw dipyn back o yrrwr ydwyf ar rheilffordd ym Mhort
Mynd a steamers i 'Stiniog, wel dyna chi sbort
Ond daeth (struggling to remember the next two lines)
Mr Pollock a ddywedodd dwy y gant y gewch chi
Wel, ie fel petaswn, coeliwch chwi byth
Mr Pollock, wel ewch ar eich beic
Os dwy y cant yw y cynnig
Bydd yr hogiau ar streic!
I'm a bit of a driver on the railway in Port (Porthmadog)
Taking steamers to Ffestiniog, there's sport
.....
.....
MrPollock said you can have two percent
Well, you wouldn't believe it
Mr Pollock, get on your bike (a topical reference then)
If two per cent is the offer
The boys will be on strike!
Not going to win a Nobel Prize for literature (at least bike and strike rhyme), but an example of a dispute on a heritage railway.