the trouble with my laptop is that i can't even get into the live cd!
Okay, let's look at what you said earlier.
using yumi or unetbootin i got several options at boot so firstly i ran 'boot from this usb' ...it is this that brought on the black blank screen, as does choosing 'live cd' when you get the boot screen if you try to install from a cd.
Which is it, yumi or unetbootin? As I understand it, yumi is a Windows program that
"can be used to create a Multiboot USB Flash Drive containing multiple operating systems, antivirus utilities, disc cloning, diagnostic tools, and more. Contrary to MultiBootISO's which used grub to boot ISO files directly from USB, YUMI uses syslinux to boot extracted distributions stored on the USB device, and reverts to using grub to Boot Multiple ISO files from USB, if necessary."
eventually by trial and error i get some kind of interactivity from the usb options if i choose 'safe mode'
Here is what the boot options are for the KDE MiniMe iso.
Which options do you see when you boot?
Which options have you tried? We cannot see what you see. You have to be specific in saying not only what you see, but what choice(s) you make. No one can offer intelligent suggestions or advice if you see an elephant and describe a pillar or a rope.
the system tries to load up and the screen gets as far as 'localhost login' then pauses for awhile (in video safe mode it gets this far and stops dead)...then i get a blue background screen with some ms-dos typing which says 'x server unable to start graphical interface would you like to read output' or something similar...i then get a page of gobbldygook with 'exit' at the bottom.
If you are getting the "blue background screen", then you have almost successfully booted to a working desktop. The problem lies with the video driver, and the live CD is attempting to sort that out for you. Again, choosing
which option gets you this far? If you get there again, choosing the vesa video driver will at least allow you to get to a desktop. Then you can work out the video options from there.
I can visualize what you are seeing, having seen it before. But you haven't said enough about
what you are doing to get to that point. A "page of gobbledygook with 'exit' at the bottom" is not an accurate description.