Honestly, for most setups I would recommend LMTP nowadays. I don't use Postfix, but that page looks good: http://wiki2.dovecot.org/HowTo/PostfixDovecotLMTP

You do not need to do anything special in postfix, if you use Dovecot's LDA or LMTP, when you change the storage backend. Most importantly, that way you can let UserDB return a different mail_location per recipient without postfix knowing anything about the difference.

Thank you Steffen, I shall give that a go and report back with how I get on.

-Mark