UPDATE!! This worked it just took a very long time for the wifi to connect! (About 25mins)
I followed the link to the public lab pi builder site. I then followed the download link to GitHub: https://github.com/publiclab/pi-builder/pull/53.
I followed jywarren's download instructions through to gitlab. (I have never used gitlab before so this is probably where I went wrong!)
I downloaded the artifacts zip entitled 'camera_web' which gave me a zip file and an img.zip.sha256 file.
I unzipped the other and used belenaEtcher to flash these onto my SD card.
I waited 10 mins from plugging in my raspi for the network but nothing showed. I've attached screenshots of my process - any ideas where I've gone wrong?