Wow, thanks so much for all the replies! I am almost glad to hear that this is a recognized problem, I was beginning to think I was crazy or that my guitar was at fault.
@ Old Potter, I don't think the guitar has a wolf tone, this has just happened with these 2 sets of strings; but on my previous guitar I found the same problem.
@ Alan Carruth, that is a very detailed & to arcane explanation, thank you!
@ Hanredman, there does not seem to be any option in this country, it's D'Addario or nothing
I find I can't play medium tension strings, the higher tension seems easier - very counter-intuitive! Nice idea re wearing a g-string, haha, but I fear the guitar would crumple up & die in horror!
@ Andrew Pohlman, I have tried the nylon strings, but really don't like them at all; am using the D'Addario Pro Arte hard tension "carbon" EJ46FF strings. Maybe I should ask relatives in Europe to send me some other brands of strings to try. Meanwhile I will soldier on with these until pay day