Newcastle upon Tyne libraries can now be added to the list:
http://newcastle.lib.overdrive.com/ I've added them to the Wiki list.
The selection of titles appears to be very similar to the Essex one. However the Newcastle site makes it explicit that you
don't have to be a local resident to join. We're a very friendly lot up here in Geordieland
Interestingly, the neighbouring council in North Tyneside (where I live) lets you borrow audiobooks but not e-books. Different supplier I suppose.