The Yorkshire one is/was here - https://www.google.com/maps/@53.7316522,-0.6725663,3a,75y,339.63h,85.08t/data=!3m7!1e1!3m5!1sTGPH1vo-NgE3R4I-xat17w!2e0!5s20100301T000000!7i13312!8i6656 - on this old school building, where the hanging basket thing is, next to the window, but it's appeared after this latest Street View picture (March 2010). The Geograph picture above was taken on September 15th, 2012, so it may well still be there now. The 'fence' in the Geograph picture is actually the open gate...
I was in Hull a few weeks ago and I may go again next year and spend some time at Fort Paull, to see the only remaining Blackburn Beverley, if I get the chance, I might go past and ask them why the sign is there...