Well, he poohed on Friday (it had been 5 days). Since then I've been giving him kiwifruit most days and yesterday started him on prune juice. And he's just done a great big poo! So I'm putting it down to the prune juice!
I just find there is so much conflicting advice (as with everything baby related!). I'll read something that says give fruit, no fruit, then another only veg, then only orange veg, then introduce green veg????? It's all soooo hard!!!!
But thanks to all of you that have offered a suggestion

Fingers crossed he's passed a big hurdle!