First, thanks for the photo CkyHC.
As for the other stuff:
Well wearing wolf hides doesn't make you an Ulfhednar by default. Other groups (like the Fianna) might have worn wolf pelts but they aren't "Ulfhednar". As you said, Ulfhednar were Germanic warriors who revered the cult of the wolf/Wotan/Odin while the Berserkers wore bear pelts...these are all generalizations of course. There supposedly were some who revered the boar too, though this isn't as well known. The thing is, I don't think there were any real strict regulations about this stuff.
The English are a mixture of many things, but generally speaking the English derive from the Germanic Angles, Saxons, Jutes, and some Frisians. Of course there has to be some level of Celtic Briton mixed in...they also mixed with some of the Celtic Welsh/Cornwall peoples, later Danes/Vikings, and in Scotland it was a mixture of several Celtic groups (Gaelic Scots, Celtic Picts, Celts of Strathclyde, Germanic Northumbrians, and Germanic Vikings of the islands, Sutherland, etc).