Need advice on self initiating

[foreverchangingnappies]

I started training in June (my boy was 2.5 and is now just over 3). He took to it very well and will use the toilet fine when I take him. We rarely have accidents nowadays. He always tells me when he needs to poo, but not wee.

But I need advice on how to get him to tell me he needs to go! He is very good at holding it, will hold it until I take him basically. He won't go at pre school even though they try, but equally he doesn't have accidents there. I've cut down how often I take him - now first thing in morning, lunchtime, before dinner and before bed. He definitely needs to go by those times, as when I take him he goes a lot, just doesn't want to. It's such a challenge to get him to the toilet as he doesn't want to stop whatever he's doing.

Should I stop taking him (apart from morning/bedtime) and just wait until he realises he has to go? The last time he had an accident was when he'd drank extra water and just couldn't hold it anymore, he did eventually say he needed a wee, but didn't make it in time as he was so desperate.