If I'd bothered to read the instructions Parkside kindly provided in their kit and not just looking at the pictures, I might have realised that the excellent transfers were Presfix and not Waterslide.
This makes a difference because if you cut the transfer out of the sheet, drop it in some water and then try to transfer the lettering to the wagon body, the letters go all higgledy-piggledy as you can see. Worse, poking the letters with a wet paintbrush or dragging them around with tweezers doesn't work. How they became so stuck the side I don't know but I can honestly say the bond is one of the strongest I've come across in my model making career.
The correct way to deal with these things is to cut through the transfers and peel the backing sheet and letters away. Turn them over so you can see the words the correct way around and then press the whole lot onto the body. Assuming they look to be in the right place, swash water over the backing sheet and it will lift way leaving beautiful, film-free lettering.
Simple when you know how.
Mind you, a cleanly painted model does look boring doesn't it?