I agree with some of your points. Bras OK, but if you hand wash on wash in a gentle setting they last longer. Every day bras are a necessity for most of us. Buying sexy ones is not.
Bikini wax - don't know if it's been suggested but I bought a wax pot thing years ago. The wax doesn't cost much at all. You'll save 50 quid a month right there. I also never get ingrown hairs or anything now that I do it myself, and it hurts way less (let's be honest, no one is going to be as careful with your fanny as you will).
Tights, again, hand wash and you should get a good while out of them.
Hair, I guess it's more important to some than others. I like my natural colour and get a cut maybe 3 times per year, but I can understand those who need to get professional colouring.
Occasions - women can't get away with the same couple of outfits for every occasion, but men could definitely get way with a couple of suits.
Overall, I think you are right that it's more expensive for women, but I think you could probably make some cutbacks
Edit to add, sanitary products should be counted as general grocery cost, definitely not discretionary spending