I do wonder if all counties follow the same pattern re contact. We adopted just over two years ago and we have letterbox contact. This was reciprocated for the first couple of times but has now stopped. Whether it will re-start or not, I don't know. I hope so. We will continue until our son is an adult, unless we feel (for whatever reason) it is wrong to continue.
I've spoken to quite a lot of adopters (in my area) and no one has told me they have direct contact with birth parents. I've done a lot of courses so I am in situations where we do discuss things but of course I've never asked this direct question. I have met an (adoptive) parent whose children have direct contact with a biological grandparent, and a couple of families who have direct contact with siblings.
Meworthit, re "Contact with birth family can be very important for an adopted child. It is a link to their identity and can help them understand why they are adopted. Rather than imagine a wonderful birth mother who will come looking for them one day, the child from an early age has a realistic understanding that birth mum can't look after them due to mental health, addictions, poor lifestyle choices..."
I am not sure about this statement in relation to older children, and they are (in my opinion) the most likely to have any kind of direct contact. Older children will know their parent is not someone able to look after them well, surely. Very young children, e.g. babies and toddlers would need to know this about birth family but I would be quite (very) surprised if a baby or toddler had direct contact with a birth parent.
My son's identity is not limited to who his birth parents are. They are part of his story, as are we, and we do try and keep understanding about birth family alive. Our son was adopted at three (he's now almost six), and I know it is completely important for him to be aware of his story, However, I would be very surprised if it were felt to be beneficial for him to have ongoing contact with the parents who could not look after him or keep him safe.
This is my experience and opinion based on his life and doesn't reflect on other posters who will have different experiences.