In the early days of the scheme I believe one company (might have been the met police but don't quote me) tried to take bikes back from employees and it caused a massive uproar. Since then as Amiga says I've heard of no more cases. Cyclescheme.co.uk most certainly don't want any of the bikes back. What would they do with them? Think of all the marketing etc they'd have to do to sell them.
The wording used by cycle scheme companies is what worries most people. The company can not commit to actually selling you the bike at the end at any point as other wise the scheme would become a hire/lease scheme and you could then not benefit from tax and NI savings. Now if you were really worried that the scheme might take the bike back at the end of the extended hire period if you'd read the rest of the gumph you'd have found your answer. The bicycle is your responsibility, if it were to get 'stolen' then you still have to continue any payments outstanding. So if asked to hand it back, oh look, your bike has been stolen....This will never happen though, the cyclescheme companies do not want the bikes back, if anything they want you to get a new bike on the scheme every year!
You are not paying market value to extend your hire period either, well you are but you're paying the market value of a 4 year old £1000 bike. The 7% you pay to extend your hire period is a refundable deposit, not a final payment, it's all in the wording remember! After 3years and 6months of hiring the bike you receive an email then offering you the chance to have your deposit back and you return the bike OR you offset your deposit as final payment and you then own the bike.
Credit limit is set at £1000 but there used to be an option where if a company chose they could increase this value but I don't know of any that have applied to do this.
People look far too deeply into the scheme. It isn't a scam, it offers a saving, it opens up the opportunity for those with credit issues to get a new bike paying by installments interest free. You just have to understand that the wording used has to be used to keep the benefit the scheme offers.