Advice for Spouse Application. I don't want to mess it up!

[CrisEL]

Hello,

I have been with my British fiance for almost 2 years, we met in Italy in 2012 and had a distance skype relationship until March 2013 when I came to the UK on a tourist visa (I'm Mexican, I don't require a visa to come, and I can stay for 6 months). On the 5th month I went back to Mexico, applied for a Student visa and was approved (I am currently enrolled, everything is legitimate and legal). We are planning to get married in December and apply for a spouse visa before my current student visa ends (In January 2015.) I am totally eligible, he meets the financial requirements and we rent a flat were we have been living since October. I meet English requirements as well.
Here's the catch: When we met I was separated (but still married). When I came back to Mexico from Italy I filed for divorce, our negotiations took a few months and divorce was finally granted in January 2013 (2 months before I came to the UK for the first time as a visitor). When I applied for my student visa, however, I STUPIDLY ticked the "Single" box. In part because I didn't think too much of it, I am used to saying I am single anyway and didn't think it would matter. Also in part because if I ticked "Divorced" I needed to provide a translated divorce certificate. Papers in Mexico take ages to be issued, lots of annoying red tape, and I was not going to be able to get the certificate from the council registry on time to apply for the visa and come back for my course. So I didn't gave it much thought and went the easy way of saying I was single.

Now we are engaged and are willing to do everything right. I have already requested my divorce certificate and should be ready and translated before the wedding in December.
But I am horribly paranoid and worried that my visa will be refused on the grounds that there are incongruencies between my current application and my previous student visa application.

Is this going to be a problem? Should we be prepared for a refusal and appeal? Is there anything we can do now to make the process simpler in the future (like writting a letter now and correcting my mistake on my student visa application, for example?)

Thank you very much for any advice you might give! The sooner we know where we stand, the better prepared we will be when the time comes.