AH! Thanks @Cheesus- after reading this thread last night I decided to buy some essential oils, incl Clary Sage, and I also bought Sage teabags ( I can only imagine how bad they taste!) Will report back on the results. I used oils in my 20's and somehow lost interest, but actually lavender has been such a huge help, it is worth a try with the sage etc...
If that doesn't work get an actual rosmarinic acid supplement, as the concentration will be both standardised and higher.