The Central Wales line had BR 80xxx 2-6-4T allocated for the last couple of steam years 1963-4, until dmus took over. They were allocated to both Shrewsbury and Llanelli, and worked right through, must have been a challenge for coal capacity. There was no intermediate loco depot. The type had not previously been on the WR, they were ex-LT&S locos displaced there by electrification.
When the same type came to the S&D locos were changed at Templecombe.
The big GWR tanks hauled freight, they did not have steam heating connections. Severn Tunnel Junction to Salisbury was a common turn and probably the longest. The reason the 2-8-2T were built was to give larger coal bunker capacity over the comparable 2-8-0T, some were actually conversions.
In Ireland the ex-NCC 2-6-4T, built at Derby, became common performers on Belfast to Dublin reliefs and excursions towards the end of steam, working right through and back.