I think this is becoming very dangerous and now advise against it. Firstly, she will need to get the approval of her insurer because she will not be the registered keeper of the car for 6 months. Secondly, speeding, parking and congestion tax tickets will not reach here quickly enough, possibly causing an increased penalty. But thirdly, unless you actually paid the fleet itself for the car, and that was documented, the fleet that remains the registered keeper could re-sell, mortgage, or take a loan out using the car as security in the meantime, and, if they default, the car could be snatched back from you by the finance house. I think the only way to make a deferred keepership purchase is as a proper lease contract, either with all payments upfront, or one down payment as deposit then the first 6 months lease payments then a balloon payment after 6 months.