Hi Jorge!
Basically, i did my high school (12o) in Portugal. I guess that this is enough but i also made a 3D course in Saldanha (Lisbon), an IELTS (International English Language Testing System) Test here in London, and i have a Medical Class 1 as well.
You should do a passport as our Portuguese National Identification Card (BI) has less value.
I was also enroled in London Metropolitan University on Airport Managment and Operations (Pilot's Pathway), but canceled the course as student finance wouldn't cover flying hours. I went there because of a portuguese girl that said she got her flying hours covered by student finance, which was a big lie!
Anyway i guess that you only need a passport and the High School certificate.. as for the grades i don't know what is needed, but in the British Council website is stated that our 12o diploma is equivalent to A-Levels. Now i don't understand much of these A-Levels and how do they do it here.
Goncalo