As someone who administers (administrates?) a cycle to work scheme for their employer, I ought to point out that, as remberbuck suggested upthread, the employer retains the right to retain the bike at the end of the hire period. That these schemes are contrived precisely to enable you to buy the bike at the end is kind of beside the point – but this is why finangling a remarkably expensive pair of pedals or luggage block or whatever is not risk-free. And you would technically be liable to pay tax on the bits of bike that made it cost more* than £1000.
But people do it, and I would venture that there are better ways for an employer to go about building up a fleet of pool bikes than to end up with a motley selection of sizes and types. Perhaps I'll look at retaining just the Bromptons that people hire. ;-)
I wonder if anyone has ever paid to extract themselves from the scheme before the end of payments? Or handed back the bike before all payments?
I think the only way to do that would be to leave your employer. You have to sign a contract, after all. And then you'd probably find that the entire outstanding balance was taken out of your final paycheck. I don't know if anyone ever did that voluntarily, unless the bike was a really poor fit or something.
* This is why I dislike the HMRC arrangement, because while a grand still buys you a very nice bike for riding to work, that certain bikes, like Bromptons, are leaping up in price year on year means they are becoming close to unaffordable within the bounds of the scheme. I'm disappointed that HMRC hasn't seen fit to tie the scheme limit to the RPI.