Bismillahir Rahmanir Rahim.
The consensus of the majority of scholars in the UK is that together with the nikah, the couple should also have a civil marriage to officiate their marriage in the eyes of the law. An Islamic marriage conducted in the UK is not acknowledged as officially registered in UK. To enjoy all your legal rights as married couple in the UK, the couple must undergo a registry. This is highly recommended by the consensus of Ulema and is particularly in the interest of women, as it offers them the best possible protection both within the marriage, if a spouse passes away and too should your marriage unfortunately come to an end; this amongst many other rights a married couple hold dear. The civil marriage is not considered as bid’ah. It is considered permissible (mubah) to benefit and enjoy the right of a registered marriage in the UK or ones country of residence.
And Allah(swt) alone knows best.