是要等12个月

"You must be free from immigration time restrictions when you apply for naturalisation. Unless you are married to or the civil partner of a British citizen, you should have been free from immigration time restrictions during the last 12 months of the residential qualifying period."

http://www.ukba.homeoffice.gov.uk/britishcitizenship/eligibility/naturalisation/standardrequirements/

还有一些遗杂要求，可是应该都是楼主相当然就满足的。

入籍需要多长时间处理就要看运气了。最短几周，最长半年。我做的时候一个半月就批下来了，办护照也比较快。