Agree with natural end - that's the problem, his current school has the natural break at yr 2, so he'll be top of pre-prep then, and yr 3 is the start of prep. Would have preferred though pre-prep ending at yr 3.
My dd was a flexi boarder (Mon-Wed, Thu-Sat) in yr 3, but ended up asking to stay so we would go and see her every Wed/Sat/Sun even if due to activities she chose to stay at school.
He goes for sleepovers at lots of different places (friends/grandparents) so no problem with him going away.
Age wise he's an October birthday (as is my dd) so they are the older ones in the year. So 8 rather than 7 for majority of yr 3.
Wouldlikeagirl personality wise my ds is a very calm controlled lad, and is not a risk taker. He will calculate and assess a situation before undertaking anything. He is a musician, and a sports player. He is above academic average but is dyslexic.
His request in a school is that it is small, no girls, with plenty of football and rugby, with a piano to play, and would like to sleep there.
My only concern with boarding school for him is that he doesn't throw himself into everything, he's too controlled. His sister on the other hand didn't care what it was that was going on, she was just there in the thick of it getting on with it.