Click the link. You can't become a specialist without becoming licensed (officially registered with the GMC). It's the same in the US... you can't specialize without a training license.
Better yet, if you aren't going to do your own research, don't bother. The fact is, unless you are an EU citizen or you are earning an EU diploma, it's almost not even worth trying. People have done it, yeah, but it's not like plastic surgery is some easy specialization to get in the first place.
"When I haven't any blue... I use red."
- Pablo Picasso