Firstly, no - but having said that, as we know, the g'ment can introduce legislation to do anything if the circumstances are extenuating enough. But, assuming nothing dramatic and unforeseen had happened, military veterans pensions already in payment are safe. Your 'pot' is pre funded by the g'ment, so don't worry, the principle by which it is paid out is safe. If money in circulation ever did run short, the g'ment would simply print more money (and introduce inflationary risk), just as they woud have to do to cover State pension benefits. The amount your pension pays each month could drop, but that would be because it might be linked to an index which, in turn, is deflationary. It would be a brave or desperate g'ment which would mess about with the military pension..
Try and find an IFA who ideally, has a military speciality/knowledge about AFPS 75 and 05.