Hi Dave,
I'm currently building HMS Suffolk 1/96th based on the Dean's Marine hull. I've posted some of the build on the Dean's forum.
The references I've found useful are-
Man o'War 1 County Class - lots of photos of all the ships plus drawings of Suffolk.
Raven & Roberts British Cruisers of WW2- much the same info as above
Profile Morskie- HMS Kent has reasonable drawings, they can be corrected from photos, the basic structures are there.
Norman Ough Plans of HMS Dorsetshire - these have profile & hull lines for the Norfolk Subclass, plus lots of deck details, fittings etc that were common to all three subclasses. (These might be best for you if you're interested in Northumberland)
Shipcraft- of some use, some interesting photos but the drawings are restricted to plan & profile.
I can't remember which motors I used- they are screwed down inside the hull with the labels covered! Possibly Kondors from Dean's Marine? They are on 6V supply.
Hope the build goes well
James