https://clic-uk.org/ is one forum that i know of. However it is not as good as here as a) they tend to ask for your phone number b) if you say you ODed the mods will phone the police and ambulance and c) it's read only mode between 10 pm and 8 am UK time. Although I am registered I don't tend to use for the fact they overreact. That's the one good thing about here as nobody phones for an ambulance/phones the police. I personally wouldn't recommend them.
I am a member of another forum again wouldn't recommend it as they aren't so strict as here/borderline pro, especially when it comes to ed. Certainly content which is banned here (for example mentioning how much someone eats in a day) is allowed there.
I have found that with other mh forums they are either too strict or (borderline) pro ed/sh. That's what I like about here it's got the right balance.