Certidão de União Estável

Hi!

I am a Brazilian citizen currently studying in Italy for a PhD (with a regular italian Visa). My boyfriend (who is an Italian citizen) has recently moved to the UK to work there full time. Since I am in the final part of my PhD I have the possibility of visiting him in the UK for long periods, and this is actually what we would like to do. Unfortunately I cannot stay in the UK for extended periods.

We think (hope) that getting a so called Certidão de União Estável will allow me to get some visa to stay in the UK as long as I want and work.

Though, we are not sure that this will be the case, and of course we do not want to get this Certidão de União Estável if this would no serve our purposes.

I am wondering if you advise me on this or maybe point to me some advisers that could help us with this regard.
In case you need some more information on "Certidão de União Estável" in order to point me to the right adviser, please let me know.

Thanks a lot for your time.