https://www.bbc.co.uk/news/articles/c4gdj2epe04o
the report is very much a game of numbers but what is clear is that Heathrow is expensive and will get worse in the next few years. And the passengers will pay. And whilst Virgin are being very vocal they aren't suggesting that they will divert flights, because the passengers want Heathrow! Well they think they want Heathrow, mainly because it's the place the experts in guidebooks and websites tell them.
But maybe visitors might lke to check whether Heathrow really is the closest airport to where they want to be, and if not, can they reach the closest reasonably easy from where they live. So if you do eventualy have to pay Heathrow rates you will at least be sure that there wasn't a better option