Hi,
as promised, I am back with a progress update.
Unfortunately it still isn't resolved. It turned out not to be the template plugin as when default Joomla template enabled its still same issue. It seems to be that the server is rejecting the cron jobs and throws 500 errors. Someone suggested it may be a user permissions error but I don't know how to check or correct this (what the command lines are for Terminal). Someone else suggested it may be a timeout issue causing it.
My question is, what would be the commands to check/rule out the above to potential causes? What else might cause the cron jobs to be rejected?
Finally, what does the jailbreak error I initially mentioned mean? Could that be the issue?
Hope someone can help as its nearly 3 weeks on and still not able to get the crons to run automatically.