Typically I had just finished it when I discovered that right clicking in the Data Browser reveals a number of 'Show...' options, enabling these lets you see everything the Reflection class can! The Data Browser instantly becomes much more candid and useful.
Interestingly, alongside the various Application objects theres one called 'onlineservices' which it can't browse. Attempting to reflect it with script uses just marginally more memory than is available, apparently, and so fails.
I guess AE just has to hang on to some secrets
If anyone's interested my reflection script is available here:
http://chrishatton.homeip.net/?page_id=22