Some Muftis in UK say that if the husband initiates divorce proceedings in a kaafir court, the decree of the court will be a valid Talaaq.

Answer

They speak nonsense. The 'divorce' decree of a kaafir court is not valid in the Shariah. If the husband initiates 'divorce' proceedings in a kaafir court, it will apply to the kuffaar legal marriage which the court's decree will annul. Never will the kaafir's decree annul the Nikah. The argument of some muftis is baseless.