I would be extremely grateful if someone could help me with the following query

I am an Irish national who will be moving to the UK and, hopefully, my Chilean partner will be able to come with me. We have been together for four years, and will have been living toegther for two years by the time of the application. Unfortunately, it is proving rather difficult to document that we have been living together for two years.
So, we are considering getting a Chilean Civil Union. Would this be recognised as a civil partnership in the UK and by European law (we are a hetrosexual couple)?
Thanks!