I was married in Kiev, Ukraine, now I want a divorce. Is the marriage legal in the UK?

I was married in Kiev, Ukraine in 2003. Thw ma whom I married was born in Kiev. I am a resident of the UK. In 2005 we seperated. I now have a child to my partner of 4.5 years. I would like a divorce my solicitor has hit a brick wall she needs a copy of the Marriage Certificate, I have exhausted every possible way to obtaine a copy. I dont even know if my marriage is in fact legal in the UK.