Eventually I found the time to dust off the router and fire it up. Here's the nice clean 15mm* deep pocket, after a bit of chisel work to tidy up the floor:
There's a tiny bit of tear out, that will hopefully go unnoticed in the final product, otherwise I'm very happy. Most importantly, it fits the heel like a glove. I can gently persuade the heel in with a clamp and it holds firm without being impossible to remove again.
So next step is to rout for pickups and shape the body blank - and hope Santa brings some nice hardware!
* Intentionally a bit shallower than standard for reasons that will become clear later.