I believe you may have to use your back-up plan, and do a distance-learning course. The CAA would have the definitive say on this, so try to contact them in the Safety Regulation Group. It does sound a ridiculous situation that should not exist under the JAA, but there you go.
A large part of the CAA marking problem is that a lot of the questions are being cancelled or queried in the UK, so time is taken to check, although perhaps too much. It does, however, mean that unfair questions are either removed before the exam is set or credited to all candidates.
The centralised system is a nuisance, but it does allow us to send one student to an exam (we often do for people who have studied here or elsewhere, failed the exam, then come here for private tuition), without having to pay for an invigilator to himself or herself. Overall it is probably the best compromise that can be implemented yet. The CAA has assured us at the groundschool that they are working on a system with many more centres and much more flexibility of date.
Best of luck!