Just found this for Nov 2009:
RAF trained UK regular strengths and requirements by NATO rank Requirement vs Trained strength
OF-6 and above 100 vs 130
OF-5 290 vs 330
OF-4 1,130 vs 1,230
OF-3 2,420 vs 2,540
OF-2 and below 4,720 vs 4,260
Officers total 8,670 vs 8,480
See
House of Commons Hansard Written Answers for 10 Nov 2009 (pt 0012)
I guess this answers the current "rebalance" policy of less promotees...