@Celia I took out the RH needle and realigned the LH needle and it works!!!!
Can't overstate how grateful I am to you and the others who have taken the trouble to help me with this.
Attached is a picture of the 3 thread overlock which looks absolutely great :thumbsup:
I have decided to put this up for sale on a spares/repairs basis as, even though it works, the bellows don't seem to be effective so the loopers have to be hand-threaded.
My dilemma now is to decide how much I should ask ... am I allowed to seek opinions from experienced users of overlock machines on which might be a fair price?
Thanks again.