For OAA it says on their website the following (for those interested);
Candidates who are interested in this programme must also be available to commence training between Autumn 2015 and Autumn 2016 as it will not be possible to defer a place on a training programme beyond this timeframe.
Sounds like it is different for FTE, though.
Edited:
The BA FPP website states the following;
When will training courses commence?
The courses are likely to run over a 12 month period, with the first course expected to start in Autumn 2015 and the last course expected to start in Autumn 2016.