I am really surprised to hear from you that Nikah would pose a problem for you in getting your family here. Frankly, I don't know how many Muslims have gone through a Civil marriage. Almost all of them go through Nikah and that includes myself. I suggest you get your Nikah translated into Arabic if it is not already in Arabic, get the translation attested by relevant authorities in your country and also by the Qatar embassy in the UK and you should not be facing any problems. Suggest you contact the Qatar embassy in the UK for proper guidance.