Premier Inn's I am sure accept walk-ins. Even as a resident I have just walked in and paid in the morning (there is no discount for pre-booking as far as I can tell, other than if you do the dinner and breakfast deal) and I am sure I have seen non-residents do the same. I have found them a little mixed - the one I used in High Wycombe which had the restaurant within was OK, the one in Cheltenham which used the next TGI wasn't so great (maybe it was the ambience) whilst I have stayed in one a few times in Tewkesbury which had a Brewers Fayre which I rather enjoyed (sadly unlikely to go back there as it was work related and we no longer have an office nearby as we did)
As for the forum idea, I can see Mojo's point - would you do one thread per venue, or per location? How would it be ordered, as forums do them in date order. I suspect the Fares section was planned as such so that the order was correct for all the sections but that area isn't dynamic like a venue section would be. If anything, a Wiki style site may be best suited to such a venture, but then, doesn't it just become another (but smaller) Trip Advisor?