I would like to appeal to our "brothers across the pond" if I may. Then again, this is pretty much for anyone who has knowledge on the subject and may chime in if they so wish.
In 1991 Genesis released the album We Can't Dance. This song (DTLS) was featured on this album and is a amazingly constructed song musically as well as quite depressing lyrically. I was thinking about this quite a bit until I re-opened the liner and in the notes above this song read the following: In the early 1800's, large groups of mainly unskilled labouureres built England's Railways. The cost in human terms alone was very high..."
In comparison to The US, what kind of figures did they mean? How much worse could it have been in comparison to what we had lost? I realize this isn't quite a preservation question but just wanted to put this out there. Granted laying track back then for either the US or UK without the modern technologies we have now i.e. GPS and so on, was deadly but which side had it worse?

This master's thesis will tell you a lot about English railway construction crews. I borrowed it through our academic network, "Ohiolink".

Wilson, Carlton Eugene. A Portrait of the Life of the Railway Navvy in Great Britain, 1830-1855. Ohio State University, 1980