Potty Training Woes

So my son has been really good at doing a wee on the toilet/potty for months now if we put him on it. He won’t hold in a wee but goes a long time dry before going on the loo or in his nappy… The issues are he won’t tell us if he needs a wee, he’s just fine with doing it either way. And the real issue is the poops. He’s got great understanding but when I explain about needing to tell us or doing a poo on the toilet he just looks at me blankly. I can tell when he’s due a poo because it’s usually once a day and he’ll do lots of trumps just before. Frustrating thing is I’ll put him on the loo, he’ll insist he’s all done then a few minutes after getting off the loo he’ll poo in his nappy 😤 I’ve asked why, asked if he’s scared, asked if he wants to watch us, bribed him with a new toy and chocolate and nothings working. Anyone encountered this or can suggest anything I might not have tried because it’s driving me crazy 😂 There’s no rush as such, just he’s a pain for nappy changes and they’re bloody expensive so the sooner he’s out of them the better 😂