I notice this post is a year old (well nearly), but thought I would add something.
I think you may have to go through National Archives for this information, but not 100% on this. However, I suggest you take a look at their site or if in UK you ring them and they can guide you.
Don't hold you breath though, my grandfather was with the British Embassy in Moscow and no they cannot give you that information or won't for some reason and refer you to everyone and anyone. I too have full information on my family member, but it is of little support.
I have spent hours and hours and all that goes with getting translations from English to Russian and in the end Moscow Archives turned out to be brilliant in their help. Waiting currently for the marriage certificate from Russia. It does not match anything like those of the UK, but gives a lot of information.
You could try the Italian Archives if they exist or on genes site they have an area for overseas marriages. If you care to respond with some details, I will be happy to have a look although Ancestry may have these too.