Thanks again, Minto77, you really are a mine of information, as I recall it most definitely was an hotel, with dining room, bar and all that, as well a quite a number of (rather gloomy) rooms and a central-ish staircase.
Brown paintwork comes to mind, but that's not a lot of help, most things seemed brown then. We only stayed one or at the most two nights, on the way back down into England, and we booked through a tourist Information service when we decided that we'd travelled enough for one day.
It was I think very greyish, rendered possibly, symmetrical and I think 3 or possibly even 4 floors high - I think our room was on the first floor, above the dining room / public rooms, and I'm sure there were other floors above.
It's silly, but I was determined to try and find it when we ended up back in Hawick again. I think that on that evening many years ago we didn't realise there was so much more of the town than a short stroll round in the immediate area after dinner, showed us - some shops, all rather traditional and similar, on one or two streets nearby, in one direction, and, as first I mentioned, quite a sizeable bridge on the right hand side, a short way away, I think, as you stood at the front door, but well within sight.
I really think you may have been on the right track with the name "Station Hotel", and can't prove that the place we stayed was "the Commercial Hotel" - but for some reason we both thought that was what the place we'd stayed years ago was called.
Thank you all for your helpfulness with our nostalgic ramble looking for Memory Lane!