I finally managed to extract Tariff information indirectly from ukpower.com (if you request a comparison quote, you can click on an individual estimate to view the appropriate tariff).
Its doubtful this is completely up to date (the numbers didn't match those I was given over the telephone by Powergen themselves), but its a start nonetheless.
Confusing customers by misrepresenting energy tariffs is really easy. For example, when a supplier quotes two rates - one for the first x units consumed, and one for units consumed above x, they will not tell you over which period the 'x' units must be consumed. Some tariffs (like the one I was quoted over the phone by Powergen) was based on consumption of 'x' over a quater. Other suppliers (like British Gas) quoted a similary tariff where 'x' was consumed over a year!
Really difficult to compare in these circumstances!