I just noticed the copy setting for voicemail to email is not working at the time of writing.
I tested with a Fongo Mobile and Freephoneline account.
If anyone is concerned, I've tried to notify Fongo.
Voicemail message waiting indicator triggers relatively quickly, however. The email just never arrives (or at least, I've waited over 30 minutes with the FPL account and over 30 minutes with the Fongo Mobile account).