I've removed the sleep. By way of background, as mentioned above Westpac's CSV export backend is pretty crude. Extensive testing demonstrated the incorporation of a one second sleep ensures more predictable step sequencing. Note it is impossible to run concurrent requests to Westpac's CSV exporter as well (it detects this and forces you to confirm the request you want). 

Nevertheless I did another couple of tests this morning and Westpac's backend right now seems to not require a sleep. Perhaps when it gets heavily loaded we'll see issues, but I'm fine to leave it out given it's of concern.

Note I run this script daily at 6:00 am and it's never failed once since I pushed my commits. So that's encouraging as to its reliability.