@Silkieschickens the standard NHS protocol for de novo Stage IV breast cancer is direct to endocrine therapy (letrozole and a cdk 4/6 inhibitor like palbocyclib, denosumbab for bone strengthening, and if you aren't post menopausal, an injection to stop the ovaries) and surgery is no longer an option. I know it seems weird, but at that point it's important to get the distant cancer under control and a surgery and recovery would delay it. A mastectomy manages local disease to prevent it from spreading, which at stage iv it already has.
However, adrenal gland is not a real common place for mets (though you are lobular, which likes slightly odder places than ductal) and if the common places are showing clear that's pretty favourable too.
There is also a growing school of thought/research/practice in stratifying stage iv patients and treating those with limited metastatic sites with local therapies in a whack a mole type approach to achieve lower tumor burden and longer term remission between mets flare ups and manage endocrine therapy resistance. But.. Not standard of care here, at least in the NHS.
If you do turn out to be stage iv I would suggest seeking a second opinion either from a top notch French hospital or via a private top notch UK consultant (preferably with breast cancer research focus like at the Christie, etc) as to treatment. Some US super cancer centres like MD Anderson or Dana Farber also do remote second opinions for a cash fee (which if I remember correctly is about what a UK private consult would cost anyway), which you can book online via their portals. It may give you peace of mind that the direction set is the right one or possibly provide a different option that you may need to go private to obtain.
Unfortunately your experience Friday is not unusual, I went through something very similar. I never felt more like a statistical hunk of meat until I went through that NHS diagnostic process.