Changing my name on my passports

Hi everyone, I'm Noor.

I'm getting married to my fiancée in Scotland in 2016, and we've been living in Sweden for three years. Once we are married, I intend on double barrelling my surname to add her's on, and I'd like some advice on how you go about it. I'll need to change my name on my British passport and documents, as well as my Pakistani passport and NICOP, but since I'm having a same-sex marriage, I'm not sure if Pakistan will even consider us married.

Thanks in advance!

LoL