Personally, I would keep it simple and straight forward and say "I require sex." Takes away the 'hidden agenda' hook they like to hang their hat on, and passively aggressively punish you with, for not being brutally direct and straight forward.
GP told me that he told an LD GF "I am a grown man and I will have sex.". Personally, I like that better than "I will not stay in a sexless relationship" or "I require sex."
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver
