Park Lodge / 1a Mounton Rd and Regent House are roughly at the junction of Thomas St and Mounton Rd.

There is a history of nursing / small hospital / work house /social housing in this vicinity.

I would not be surprised if "1a" was an annexe to the Poor house /Work house ( Regent House is all that remains today) http://www.workhouses.org.uk/index.html?Chepstow/Chepstow.shtml

http://www.geograph.org.uk/photo/205666