Hi Joel thanks for your feedback - im confident I can get this running with the benefit of your experience! Ive been using the a2ensite command which seems to create the links you describe between sites-available and sites-enabled.
Can you give a little more explanation of the .conf updates you describe - some lines are commented out and some lines seem to be repeated betwen the 2 paragraphs of code (im good with putty/ssh/vi etc btw - its just making the correct updates to the config files that im failing on!)
also i need to make sure im correctly understanding what HTTP_HOST, INTERNAL_IP, 192.168.10.4, REQUEST_URI, INTERNAL_IP should represent - i will go and do my own digging but it would be great if you could clarify
thanks in advance