DS was at that stage late last year, he wanted to wear undies, but then would just pee in them, come and ask for a new pair

He toilet trained himself basically about a month ago. He has had about 5 accidents all up. Mostly poos.. LOL.. but is now pooing in the potty as well.

I realised that he just wasn't quite ready, and I wasn't willing to push him in any way. Plus I hate cleaning up wee and poo.. LOL

I would say wait a few months.