Chris,
Looks like the back tyre could use a puff of wind!
Both the U and the W had valenced mudguards, upright handlebars, and foot boards. Besides valences, the W also had side extensions or wings to the front mudguard, clutch, and kick starter. It is had to say, but this does not look like it has the side extensions to the front mudguard, nor do I see any hint of a kick start pedal. So I think you are correct in thinking this is a Model U.
-Doug