Cheers James!
The funny thing is, that your comments above are the answers to the questions I wanted to ask you after your CamelOne keynote (but I didn't mange to grab you before I left the conference). I'd had the same thoughts about using breadcrumbs and ElasticSearch. We'll definitely take a look at the resources you've provided and most likely get back to you once it's sunk in.
Thanks again,
Paul.