Thanks ever so much Guix, it has been solved by generating an additional character in the font.
To make it easier for others that may come across this, I have linked to the ammended DefaultFonts.c file leaving the original font in tact. Just change the font name in your main code from 'SevenSegNumFont' to 'SevenSegNumFontSpace'.
http://www.networkedsolutions.co.uk/arduino/DefaultFonts.c
Thanks again for your help and guidance 