Thought id share this as a number of people are interested in the overlockers!
It runs over 2 days for 2 hours for £30. I’ve signed up for it myself 
https://lewisham.gov.uk/cel/courses/tfd0506br---machine-skills--learn-to-use-an-overlocker---81036
Overlocker course: Lewisham Adult edu 7h Nov
Mysteriously not there anymore! Our you might be right that you have to log in first.