Ah-ha! You gits! i figured it out myself:

My font file file: "LED.ttf"

1) Moved it to /usr/share/fonts/nokia (where i had spied other fonts)
2) Ran fc-cache in Xterm
3) Ran fc-list to confirm it saw the LED.ttf file
4) rebooted and hey presto.

Techniques used/learned:

1) You need root. So get easy root or whatever.
2) To move file about in Xterm:
"mv LED.ttf /usr/share/fonts/nokia" (case sensitive....i think)
3) Also handy....list folder contents + hidden files = "ls -a"

All this just to get an LED font for my clock.
Out.

(Seriously though....thanks for your help, wouldn't have been able to do it without the support of members on this forum!)