Pway or off track thinking of relocating down there in future so want to find out where to look
If you have a specific town in mind, you can always use google maps and street view to see if there's a NR presence of some kind. Generally NR P-way depots will be located at larger towns, junctions and major stations. However they won't be too close together. S&T depots will tend to be located near major concentrations of equipment. Exeter, Plymouth and Penzance would be the first places I'd look, but Liskeard, Par and Truro might also have some NR presence.
Also, have a browse of the NR jobs website, as advertised vacancies may well state the range of depots they're looking to hire for.