So, having pulled most of my hair out, I decided to start back at the beginning. I redid the iso using unetbooting. What was different this time, I dont know, other than I reformatted my usb stick after using the PCLOS live usb creator to go back to unetbooting. I tried default load live image, still command prompt, but this time on selecting 'load fail safe/safe mode' it worked, got into desktop, all be it at 1024x768, but did allow me to change it 1280x...... I'm stumped as to explanation. bad usb stick? did the reformat do anything? Anyway, problem solved.
Many thanks for all advice, suggestions and help guys. It's been a good learning curve.