The Google Sheets action only supports adding a new row.
If you need to update an existing row, you would have to turn to (a) custom scripting or (b) external automation tools which are low-code.
Personally, I like using Make.com (formerly known as Integromat) for these purposes.
I am also an Expert+ Partner of Integromat/Make, so if you need help with implementing this and you have a budget for your project, feel free to reach out to me through my website at scottworld.com:
Hey @George_Kimpton-Moss -
We have 2 helpful Google Sheets functions in our On2Air Actions app that can do more than the basic Google Sheets integration in Airtable.
The 1st - Google Sheets Export - allows you to set up a template in Google Sheets and it will automatically add your Airtable data based on whatever trigger you set.
The 2nd is a full Airtable to Google Sheets sync where it will sync your entire table each time.