Thanks Joe,
My plan is to set my coin and start buttons to clear and enter. The upper button is most commonly used, so will map to first of my 8 buttons, then will map remaining numbers to 7 remaining buttons. This won't work with all games, but will hopefully get me through until this arrives - https://atariage.com/forums/topic/334580-a-new-controller-is-coming-soon/
Again thanks for your help.
As a little aside, my first job (as a 10 year old!) was selling Intellivision, Atari and Commodore 64 consoles and games at a stall in Flemington markets in Sydney. I would use my pay to buy games for my Intellivision, so this will bring back some great memories.