dear sir I am a muslim got married to a christian woman who was divorced before in a registry office in london (non muslim office),in front of her family and the presence of over 20 people who wittnessed the cermony but withowt my family who couldnt attend ,there was only on muslim friend who attended the cermony and signed the document with her sister as wittnesses.We didnt doit in a mosque after that is my marriage valid

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

According to the four Schools, (two) witnesses are a condition for the validity of the marriage contract, most of them are of the view that it is an obligation to have witnesses at the marriage contract, but the Maaliki School of jurisprudence is of the view that it is an obligation to have witnesses when consummating the marriage. Of course, here we are talking about two trustworthy witnesses. Therefore, if the consummation of marriage took place before having witnesses, then the marriage should be invalidated, but the jurists of the Maaliki School of jurisprudence sated that the spread of the news of the marriage among the people before the consummation of marriage has the same validity as the testimony of two trustworthy witnesses, and therefore, the marriage is not invalidated.

Hence, according to this view, if the news of your marriage to this girl was spread among the people before you consummated the marriage with her, then this marriage is correct.

Finally, the two following points should be mentioned:

1-    A Muslim should ask the scholars about the rulings which he is not aware of before acting, especially in regard to marriage and the like. 

2-    A Muslim should not marry a woman of the people of the Book, even though it is permissible, as such marriage could lead to many disadvantages, especially at the present time. For more benefit in this regard, please refer to Fatwa 89418 and 84724.