Weather forecast says its going to be cooler than average temps for October this coming week, after that, it looks like more normal temps, but yes, I'd harden them off, carefully and slowly if the temperatures are going to be lower than average, aiming to get them planted by end of this month. I might have given different advice if you were in Scotland or far north though,but where you are, should be fine - its only early October and even lower than normal temperatures doesn't mean freezing - just choose a milder night when you get to the point of being able to leave them out overnight prior to planting.

They readily self seed in the garden so follow the hardening off advice from bamboo.

Thank you both for your very useful advice.