Thank you so much brian.
The main reason i wanted to change the default currency, was so that the users do not see the USD price as the first price when they come on the site. Given that most of my clients are not US based.
I didn't want to have to lose previous invoices etc, so I tried to find a solution around it.
My solution was to maintain both pricing in USD and CFA, and then add a geolocation hook, whereby, customers outside of the US are shown the prices in CFA directly. This worked for me.