Venusian Broon's idea of pretending to be shipwrecked certainly offers the best chance of survival. There are various historical examples of such mysterious arrivals, eg the Green Children of Woolpit, and the woman washed up on the coast of Japan in some sort of round container that sounds like a modern life raft.
Ditch the mobile phone for sure. And thanks to our "nanny state", we British can't even carry decent knives any more- how insane would that seem to the 11th century? Almost all the knowledge and even practical skills possessed by any modern individual would be utterly useless, even if the language was learned quickly. For example, even if knowing the formula for gunpowder gained you royal favour, it would be little use if you couldn't also cast a decent cannon that wouldn't blow up. I reckon archery and fire making would be the most useful skills- you could live off hunting in the forests which then covered most of England. If you wanted to integrate into society, then for men blacksmithing would be about the most useful skill, as techniques and equipment don't seem to have changed that much. For women, midwifery- you'd achieve massive improvements on contemporary survival rates just by washing your hands and boiling your scissors- but to retain your Dark Ages credibility you'd need to recite some special prayers while so doing- let them ascribe your powers to a saint rather than to some eccentric habit like washing.