A Brief History of Mercia
Oops, seem to have lost the content...
Will return, after looking behind the sofa, under the bed, in the cupboard, sure I had it only a few minutes ago, is it behind the pringles?
If it helps, I have a good map of Mercia during the Dark Ages

The image above shows the extent of the Mercian boundaries at their greatest extent (7th to 9th Century).
The area in dark green at the centre shows the original boundaries of the 6th Century Kingdom.
Previous page: Map of Dark Age England
Next page: Mercia and the Danelaw