Demand outstripping supply.
It's a good thing in all cases except where the supply in question is time. This says a few things though; the first is that Britain’s people were so prepared to take part in their nation's governance that there the polling stations were unprepared. (Alternately; the people planning for these polling stations were incompetent.) The other thing is that it can be considered a reflection on the anger of the populace of these areas towards either the extant government or the proposed replacements.
In other words: someone got the proles angry enough to actually get off the couch and vote. I can't see this any anything other than a positive development for the whole of the UK.