If the same rules apply as for Westminster elections, mistakes by the Returning Officer which might have affected the result can lead to a new election. There was a famous election in Winchester where the LibDem victory, with a majority of two, was set aside and a new vote held.

However there is no provision for re-voting because electors misunderstood the instructions.

This will of course be used as an excuse to attack the principle of proportional representation. Perhaps the lesson should be that we should adopt one system of PR and use it for all elections instead of having a different one for each type of election (especially if more than one is used on the same day).