MoD website give this figure:
01-Jul-1944: The RAF reaches its peak strength of 1,185,833 personnel (1,011,427 men and 174,406 women).
http://www.raf.mod.uk/history/rafhis...meline1944.cfm
BBC history website states "the RAF reached a total strength of 1,208,000 men and women, of whom 185,000 were aircrew. About 70,000 RAF personnel were killed."
Source:
http://www.bbc.co.uk/history/ww2peop...a6649248.shtml
Looking quickly at my pen and paper sources, I can't find anything to contradict or confirm these figures.
Maybe the BBSU or Statistical Digest of the War has something else.