Withholding a cause of death

I posted on here a few days ago about one of my friends overdosing. I knew about it because she called me in between taking the drugs and dying, but the authorities have withheld her official “cause of death”, supposedly at her request. I was just wandering if that’s legal or if that’s the police realising that I’m not family and therefore not really wanting to discuss it with me,

The reason I ask is that it’s something I’d be very interested in doing if it is legal- I live in the United Kingdom and can’t seem to find information on the subject- as I’m planning on dying fairly soon myself, but I don’t want to put my ex through the stress of thinking that it’s her fault.

I’ve got a brain tumor anyway, so I’m thinking that if my official cause of death was withheld, people in general should just assume that’s what it is that did it. I just can’t wait long enough for that to actually become the case. It’s got to be sooner rather than later.