Tootbrush,
As I said before HRT is not my expertise... you have been on a lot of different progestogens though. Femoston has dydrogesterone, Evorel and Elleste Duet have norethisterone, and Femseven has levonorgestrel. Although their primary purpose is the same, ie to oppose oestrogen activity in the endometrium, I reckon they are different and can have different actions and side effects, so maybe your body didn't react well on the changes.
As I understand, the 15% of women who don't get a bleed won't have a thickened endometrium.
All your symptoms point to excess oestrogen, so maybe once you get rid of the excess, you'll be fine to restart HRT again.
One of the non pregnancy related differential diagnosis for a thickened endometrium is HRT, I think that's the cause of yours. Another one is PCOS, but I guess you don't have any symptoms?
Conolly X