No, they're not.

https://fullfact.org/law/uks-sharia-courts/

> While feuding couples have to at least consider mediation before going to court, it doesn't override family law. A court has to sign off on any agreement made after divorce for it to be legally binding, and won't do so if the judge thinks it's unfair.

> In 2013, the High Court was asked by an Orthodox Jewish couple to accept the ruling of a Jewish religious court on post-divorce family arrangements. The judge said that while the agreement would carry weight, it would be non-binding—neither party could get around English law by agreeing to abide by the decision of another tribunal.

So they're recognized in the same way as, say, a Jewish court would be, or in fact essentially any body would be?