Eric,
I have little new to add to the above comments, other than to confirm that with the prevailing westerly winds the west of the UK seems to have cloudier skies than the east. Certainly here in the Inner Hebrides we rarely have clear skies and the number of nights each winter which are suitable for observing can be counted on 2 hands (or maybe only one). Clear skies are not our only problem but winds also will affect your observing opportunities. An observatory isn’t necessarily the answer to the problem as winds of over storm force (which we get every winter) will cause structural damage or destruction to anything in its path. From all the reports I read of the observations by other astronomers it would seem that east is best, that is not to say that in the west we do not get some marvelous nights observing, we do, but I they do not seem to be that often. I hope this helps.
Martin Butcher