Whatever the truth of the matter, though, it should at least be acknowledged that the UK system is at or near one of the fairest and most open in the world. Hardly perfect: the Tories were done for campaign finance violations on the back of the 2015 campaign, and Vote Leave (or Leave.EU, or both) got fined by the Electoral Commission, but even these are in my opinion minor offences and don't or should not call into question the integrity of the results (although that hasn't stopped people from trying).
We don't have the problems of newer democracies in, for example, voter intimidation, or deliberate bribery, or just stuffing the ballot box. Perhaps I'm complacent but I think there is more reason to trust the system than not. At most a few hundred votes, out of millions, might turn out to be fraudulent, be they proxy votes cast against the will of the absent voter, or the odd postal vote too many. Each one is a crime and deserves to be treated as such, but it's a nonsense to doubt the overall result.