So why are the UK buying F-35's then?
Once upon a time, a long time ago in a galaxy far away, there lived some people with a bit of a problem. There were some big, angy bears living nearby that kept causing trouble. So all the people eventually got together and spent vast amounts of money buying things to shoot the bears with, and training to shoot bears with them. Meanwhile the bears were also spending unfeasibly huge amounts of honey on guns to shoot the people with.
One day they were sitting around in their brown courduroy flares and orange shirts, and worked out a design for a fantastically good aeroplane to shoot the bears with. Then that their men with moustaches would have something to fly when their Phantoms went out of date in 15 years time.
Then they did lots of thinking about it, and seemingly little actual work, until eventually the Wicked Witch of the West got round to actually placing an order about ten years later. Along with a few friends with funny accents, who were also buying some.
Then actual design work happened. But the bears suddenly ran out of money and started acting a bit nicer and looking a lot less threatening. And the boss bear starting drinking lots and lots of lovely vodka. But the people had already spent loads of cash on their new Typhoons, and the poor Phantoms had got so old they'd had to retire and the poor men with moustaches were reduced to flying sleds made of lead against the bears - who were no longer bothering anyway. So they had to carry on building them.
Yet another decade later the Typhoons started to turn up. Hooray! But there were no other aeroplanes to shoot down, and the men with moustaches were now being required to drop things that go bang on people who were wearing their pyjamas and dressing gowns into combat.
So they had to update the brand new Typhoons to do that, which meant the first ones that had been built went into storage, while the men with moustaches desperately looked for someone who'd like to buy them (so they could use their new shinier ones).
Then a grumpy man with a funny accent took over from the slimy man with the funny shaped face. And his grumpy friends with funny accents and a liking for Haggis were thinking of voting for new friends. So he ordered some lovely big boats from them. And the new friends built him the lovely new boats, waited a few years, then voted for the new friends anyway.
But what to do with these lovely boats with the big flat tops? Ah yes. Buy some new planes to go with the Typhoons. And so the Lightning was bought. And now the grumpy woman in charge is looking for some money to pay for the shiny new Lightnings, and decided that if people are foolish enough to put mayonnaise on their chips, they'll probably buy any old second hand aeroplane.
Unfortunately for everyone, the bears became a bit grumpier again. Although the people mostly failing to sell the newest and shiniest guns were quite happy. So the chaps have put down their beer and horrible mayonnaisey chips to have a think and decide if they want to buy new toys for their chaps with moustaches from the grumpy lady or the really grump orange man.
Does that help?