I have since revisited the script, tidied it up a bit and made it more generic – it can now cope with multiple websites other than AMSAT and Celestrak through the addition of a simple .conf file for that website.
I’ve separated the TLE and transponder updates into two scripts to enable the TLE update to run from crontab without the possibility that the transponder definition update will fail. I have yet to set mine up this way and test it (I know – not good!) but you should now be able automatically update TLEs from multiple websites with no human intervention.
The revised scripts and config files for AMSAT and Celestrak are available on github.