So I might have gone a bit crazy and had two large cups of loose green tea. It did have the expected diuretic effect.
Tbh I started not to feel good and became slightly nauseous and “off”. This actually lasted until late the following morning. It shocked me a bit because I seem to be able to have fully caffeinated coffee no problems and haven’t had nausea for so long.
I’ve stayed away from more green tea today.
Perhaps I will try one small cup every morning with fewer leaves.
I use one level teaspoon for a mug of hot water. And I drink it on an empty stomach in the morning. This is something one is not supposed to do according to my Taiwanese friend (she knows a lot about tea), but it works for me.
You could also try Japanese green tea, in my experience, it is usually milder.
It was awful withdrawing from caffeine. Now that I’ve been off it for 18 months, I’m not venturing back. I can’t see the point in it. If it’s going to trigger the dizziness hell - I’ll have to withdraw again. I’m happy with my decaf coffee every so often. (Which contains a bit of caffeine yes)
I dropped to one large cup this morning (with fewer leaves). Still the nausea came on a fraction but it is very mild. I do wonder if this might be therapeutic but uncomfortable.
I must admit, when I feel a headache coming on, if I have a coffee or chocolate the headache goes away immediately. 
it did not help dizziness when I had it though just the head pain.
Yes, MAV aside it can definitely help headaches. I don’t get MAV headaches anymore, but for example, I still get head cold/sinus headaches and caffeine and hot milk can definitely resolve those.
Nicotine works too actually, probably from its vasoconstriction effects. However, sumatriptan is probably a better long term choice (-: