When I first got my endo pains at age 35yo, I had an ultrasound on the NHS but they only did the external kind and I read online this wasn't as accurate as internal...
So I paid privately and went to some gynaecologist on Harley St for an internal scan. I think he usually did fertility scans etc, because he was telling me I had loads of eggs and everything looked great from a fertility perspective - and I didn't want kids and couldn't care less

and just wanted to know everything looked okay and whether he could see any signs of adhesions.
He couldn't. It was only when I had my laparoscopy that they found the endo. But anyway - yes - you can get them privately