There are a few SS schematics at http://www.schematicheaven.com including several marshalls and at least 1 fender.
A few SS Watkins/WEM schematics here: http://britamps.mysite.wanadoo-members.co.uk/watkins/schematics/wemwire.html
A few SS Watkins/WEM schematics here: http://britamps.mysite.wanadoo-members.co.uk/watkins/schematics/wemwire.html