I would recommand if you do really want to relearn piano, go for classes. Learning piano is not like learning guitar. Both are totally different coz piano teaches you music theory which is very important if you want to be a good pianist.

After finishing all the grades, the music school can actually sign you up for Diploma im music (you have to pay some amount) which then you can use that if you want to enroll with ICOM (International Colloge of Music), by pass all thier intro courses and jump striaght to Degree.

I have a friend who did the same thing as above so that;s why ppl start learning piano at the age of 3 !!!