Is he in a big bed? Have you tried laying down with him on his bed so he has a nap with mummy, and then get up when he's asleep? Or try napping with him in your bed and then get up? We used to do this with Jonah when he wasn't wanting to go into his own bed (cot) so we would take him into our bed where he'd be asleep within second and then transfer him into his own bed.

Maybe it's just a phase too? Jonah has phases of bad sleeping, we just got over bad nights and it's been wonderful but for a while there I thought I was going to go insane with lack of sleep.