I found it after reading this Sitepoint Thread
I have used PHPBB for a few sites and it is a pig to modify.
So, I went out and registered a new domain name and started setting up a brand new site with miniBB.
I am pleased to say that the whole Idea of customising by simply using a single common CSS is brilliant - as is the whole method of addons.
I have spent about 2 hours putting a site together so far and it is much better than a PHPBB install that I took over a day to set up and customise for even basic SEO.