SOLVED. Exorcist detective novel, set in UK, first in a series [s]

[Barry]

The book was read around 2005-2010. The book was the first in a series and focussed on a detective who was an exorcist. I recall he could communicate / see the dead and may have had a dead flatmate. The novel was set in London. I can recall a little of the end if that helps. The author was male.

[Feliks]

The Devil Rides Out (Duke de Richleau, #6)

This is a series like that.

[Melanti]

The Devil You Know by Mike Carey?

No dead flatmate, though, but there's plenty of dead people of one sort or another throughout the book...

[Barry]

Thanks guys - it's The Devil You Know