Maybe it's worth giving the Whale and Dolphin Stranding team a call and seeing if they can help and if it is relevant, add it to their records? http://www.nhm.ac.uk/research-curation/research/projects/strandings/contacts.html
Is the head upside down and missing the jaw? It's really difficult to make head or tail of it (sorry, terrible pun) from the photos without a bit of a description. Did the carcass have any limbs, fur, etc and what were they like if it did?
Could it actually have been a cow or horse?
A porpoise (or something similar) seems a possibility. I would agree with the previous post that you're probably looking at the underside of the skull. The main thing I'd note are the small and regular teeth sockets - this would fit with a porpoise and definately rule out a seal (although size would fit - a bull grey seal is pretty big). There also looks to be a lot a flesh underneath, which would be in keeping with a large blunt head. The only thing that doesn't seem to fit is size - a porpoise is a lot smaller than a cow.
N.B. The body surface looks like it could be a dead cetacean - well eroded dead whales/dolphons often take on a 'furry' appearance as the their tough hides are worn down.
I take your point, it doesn't quite fit...
When you refer to a tusk, do you mean the bit of bone at the right side of the skull? If so, is it not part of the lower jaw?
Whereabouts on the beach was this? I'm tempted to have a look just out of curiousity (as I work in Aberdeen).
What an interesting find! I found something similar off the coast of Ireland, in the end I took a section of the jawbone and sent it to the museum for identification it turned out to be a very large angler fish, i'm not sure if it would be possible for you to do something similar or is the decomposition past the point of no return haha