Fixed styling issue with blocks on Network Fronts.

The page now understands whether it is a network front or not.

This applies to www.theguardian.com - solid background colours were not showing for headings on the editionalised fronts

![front](https://f.cloud.github.com/assets/76709/862037/076c73b0-f5e3-11e2-827d-8e944ab334f5.png)