Further to this it seems that this story has been rather misrepresented in the media.
The Judgement is not that All Prisoners must be given the right to vote. Indeed in many European country many prisoners are not entitled to vote.
The point is that in the UK the sanction is indiscriminate and automatically applied regardless of the nature of the offence.
It is the indiscriminate nature that has been ruled against. It would be perfectly possible for prisoners to be denied the right to vote if their sentence was over a year for example.
More devil in the details here:
http://www.bbc.co.uk/news/uk-11676456