Not on metformin (im a T2 diet controlled), but have recently requested to go on HRT due to perimenopausal symptoms. I have been on it for a month and definitely helping with some symptoms although told it will take at least 3 months for all things to settle down.
As far as I understand, taking HRT whilst on metformin isn't an issue.
With regards to T2 Diabetes and HRT , the only warning I was given was that estrogen tablets are not suitable for T2 diabetics as they have an increased risk of blood clots and stroke, but gels, patches and sprays do not have the same risk, so you should be offered one of those, which I understand the transdermal applications are better anyway.
When I asked for HRT, I had a GP appointment separate to my diabetes review (which, for me, is normally with a nurse) - I asked for one to discuss womens health and I would recommend doing that as it gives you more time to discuss each subject, rather than the clinican rushing to discuss two separate issues. It also meant I was given an appointment with a GP who had extra training in womens health, and I had no issues getting the HRT prescribed straight away based on my symptoms.