Doesn't matter if they won or not. No party should benefit from fraudulent votes.
What's laughable about some of the anti Tory statements here is that if this was the conservatives being accused, the frothy mouthed Corbyn sycophants would be raging, and rioting in the streets with the media would be having a field day atttacking the Torys for cheating.
Setting that all aside and looking at the situation the simple truth i believe is this.
If there has been double voting, mail fraud votes, or disappeared postal votes, whenever possible the people responsible should be tracked down, fined and banned from voting ever again. Then changes need to be made to ensure it doesn't happen again. So yes this should be investigated no matter what party it involves, otherwise our entire democratic process is a waste of time.