Jenny, I have endo - I had a lap in 2013 which lasered it out. Then I was put on desogestrel POP for 10 years which suppressed it fine... Till I hit peri-menopause at 43yo and got every low estrogen symptom that existed.
I'm on HRT and have been since then. I'm doing fine. There are different options but ideally my recommendation would be to see someone privately who understands how to manage HRT and endo. Like one of the Newson doctors for eg. (I see Dr Olivia Jones.) They can experiment will all kinds of progesterone options to help suppress it whilst you take estrogen.
You might be offered a Mirena coil but my advice is not to rely on that. The Mirena works mainly in the uterus itself and if you have endo, you have it outside the uterus - that's what it is. So you need some kind of systemic progesterone/progestin to suppress it. Same goes for utrogestan vaginally - I don't think it is systemic enough.
If you can tolerate utrogestan, then you can just take higher doses of that. I take 2x 100mg capsules orally every night (continuous) but because I'm in peri, I do stop to allow a bleed - otherwise I get breakthrough bleeding randomly which freaks doctors out. You can take 3x 100mg capsules nightly, if needed.
Your best bet is not to take a combi product (like Femseven Conti) because it doesn't allow you to adjust the estrogen and progesterone separately. Use a transdermal estrogen (patch or gel) and utrogestan to start with. Use the minimal amount of estrogen you need to get rid of symptoms (2 pumps is the starting dose of gel or a 50 patch) and go as high as you need with the utrogestan to suppress the endo.
If you need more progestin, you can add in desogestrel POP - which is licensed to be used alongside HRT for younger women who need contraception whilst on HRT. But the extra progestin will suppress the endo further.
Basically it's about dialling up the progesterone and being careful with the use of estrogen. Having said that, you do need to check you're absorbing the estrogen - I'm on 5 pumps of gel and about to go up to 6 because I don't absorb it well. My serum estrogen was only 283pmol on 4 pumps. So don't get all afraid about how high the dose is, check the blood levels too...