How to safely cook a lamb's head?
My understanding is that no cooking method helps with BSE and that seems to be backed up by a U.S. Department of Agriculture fact sheet that states:


  Current scientific research indicates that cooking will not kill the BSE agent


However having a look around at a few references like BSE in sheep from the UK department of Agriculture and Rural Development while there's a theoretical risk of sheep contracting the disease it's never actually been detected. There is a related disease in sheep called Scrapie but from that Wikipedia page:


  Scrapie has been known since 1732, and does not appear to be transmissible to humans


I've never cooked a whole lamb's head but have cooked lamb brains and one word of caution is that they do cook quickly. Most recipes I've used seem to involve poaching for only five to ten minutes so it may be worth considering removing the brain while cooking the head and adding back late in the cooking process. Another idea might be to make two courses as a common theme, maybe a soup using the head and some crumbed brains.