DS was similar at about a year and a half. We just wash hands after going to the loo. Given how clean we keep the bathroom, the loo seat is safer than the front door handle, germ-wise! (I recall reading that it's more hygienic to eat off the loo than from a kitchen bench, as we're far more fastidious as a species about cleaning our loos.)

I just talked to him about what I was doing and he just trained himself through watching me and his friends. OK, so he was three and a half before he decided he wanted to go to the loo (just one month earlier he would sit on the potty for 3-4 hours, then ask me for a nappy so he could wee). He is four next week and has just decided he wants to poo on the loo. He does know his own mind! But explaining that pets and loos mean washing hands afterwards cannot start early enough, IMO. FWIW, he never liked using the potty. Always had to be the loo, and without the childseat if possible. I guess I could have saved myself some money there!