Thank you very much to all who replied to this thread. It has been really interesting to see what you all use, and given me some ideas.
I have been using the thin SotaBeams yellow wire (7/0.2mm), and have had two breakages in about 90 activations, so I suppose I shouldn’t grumble. My antenna wire doubles as an antenna guy as well, on two legs of the antenna. Inevitably the wire is reasonably taught, and I guess this stresses it.
So I have just made up my latest antenna using the SotaBeams Heavy Duty green wire (32/0.2mm), but immediately noticed the difference in weight, as well as strength. Extra weight to carry on an activation, but I will give it a try and see how it goes.
I was interested in David G0EVV’s 16/0.2mm red PVC wire suggestion as this is somewhere between the two wires I am currently using, so I have just ordered some.
Once again thanks to all for your observations and comments.