Ah yes, Monday nights at The Coach House, down the stairs, 50p entrance, bottle of Newcastle Brown in hand, great times. I first went there around 1976 to see the Knees, saw them many times in the 1970s and also the 1980s. I remember sometime around 1993 taking a couple of mates there, one of whom was a huge Man fan, and kept yelling for "My Way" at the end of each song in the hope that Plum and the boys would remember how to play it (as per Christmas At The Patti) - and they did - Brian Breeze on guitar, Clint on keyboards, can't recall the bassist, John Corbett on drums, and at the end of it (awesome rendition) my mate just kept muttering about a "religious experience", which it probably was.
As for what it is now, well I have not really ventured down Wind Street with my drinking boots on for many years, and I suspect it may be a cafe or something by now, but your recollection of it being somewhere between the No Sign Bar and the junction with St.Mary Street is as close as I would place it.