Rotherham

 One can only imagine the shock it must have been to go here from rural Roscommon in 1900:

https://www.nmrs.org.uk/wp-content/uploads/2016/04/rotherhammain.jpg

Rotherham Main Colliery

Here's another site with some pics of Rotherham about this time:

https://www.on-magazine.co.uk/yorkshire/history/rotherham-old-photos-postcards/

It looks like a nice town. Note however that the colliery and where John and Martin lived were in an area called Canklow:

The steel works and much of the worker's housing were removed for highway construction. 

The colliery itself was replaced by the roundabout. Atlas Street (from the pic above), is to the lower left, just above the 'A631' label. Canklow Road still exists, but much of the original is replaced by A630, going northeast in the pic. Apparently some of the last remaining houses for the pit workers were  replaced by the McDonalds.