Enter Pusher, an app that runs on your Mac and allows you to fire messages to devices from your desktop either via the sandbox or production server.
This proved to be very useful as within ten minutes I'd established that it was my device token at fault - it seems in that even in my dev environment running my app on my phone from Xcode I was interacting with the Production APNS system rather than the expected sandbox system, and so when sending we should have been using the production certificate.