Costs of using a toll motorway in Europe

I wrote a post here a few weeks ago about my experiences travelling between Belgium and Spain (and back) in early-mid 2008 and early-mid 2007, with details of fuel, toll motorway, hotel and other sundry costs (food, etc). Since then I have noticed quite a number of viewings of that post from people in various countries who are planning journeys of their own and I thought it might be useful to