You make a fair point but I do disagree with this analysis. Had UKIP been represented in the Commons on a proportional basis, the British public would have witnessed the brawling in the corridors of parliament which they descended to in the EU parliament, the gratuitous insults handed out by Nigel Farage and the uncooperative destructive bullying which they engaged in instead of reasoned debate. The British electorate would have seen them for what they were and they would never have gone beyond the status of fringe extremists. In my opinion it is precisely because they were kept out of parliament that they were able to present themselves as embodying a popular true faith which, in fact, nobody subscribed to in the form which they were determined to realize.
The complexity of PR is, I think, overstated. Many countries handle it perfectly well and compared to the complexity of tactical voting is arguably a simplification of the current system. Over time, an understanding of the electoral system would be a normal part of the school curriculum which would go a long way to clarifying its workings — and indeed lay the foundation for future amendments and improvements.