Thanks for the help - epgimport & https: definitely the problem.
I had to install busybox-cron (opkg install busybox-cron) and then work out where & what file to put the cron job in (/etc/cron/crontabs/root).
Then just restart cron (/etc/init.d/busybox-cron restart) and the file is downloading. Tweaked the sources file and EPG now work again.
Thanks again!