We had social services involvement at one point in the past (not because of me, because of something their dad had done).
What I learned from my interaction with social services is that the outcome largely depends on where you are in the UK, but also with what kind of social worker you are dealing.
Our social worker was very reasonable and worked with us. At the time, I talked to other women online that were going through similar things. A lot of them had social workers that were much harsher with them. A lot of it depends on the personal beliefs of the social worker.
What we went through didn't involve child removal of course, but I can imagine when it comes to child removal cases, it largely also depends on the kind of social workers you are dealing with.
Of course there are open and shut cases, for instance with drug addicted parents. But there must be some cases where a lot depends on personal interpretation.