Everything I've read has said that England had, at least until the 1800s, a minuscule black population, and particularly before and during Shakespeare.

Here are some random links on the topic since I don't remember where I read that blacks were exotic & unpopular rareties in England and next to none of the slaves passing through British hands came to the home isles:

• http://answers.yahoo.com/question/index?qid=20060913100505AAx2vYc
• http://www.angelfire.com/md/8/moors.html (to point out that mentions of Moors proves nothing)
• http://www.historytoday.com/MainArticle.aspx?m=19634&amid=19634

This book Black Breeding Machines mentions that blacks were such a small minority in England that when their presence began to bother the Londoners, Queen Elizabeth could simply order them out of the country. And it's worth noting that one of the few mentioned blacks in England is a 'blackamoor' in the Queen's service - reinforcing my rare, exotic characterization.

(And the general lack of material itself argues that there just weren't that many. It's hard to research what didn't exist.)

EDIT: As for Italy, I can only point to a similar sporadic appearance of black servants in Roman and medieval Italian sources, and links like http://www.blackpast.org/?q=perspectives/africa-and-africans-imagination-renaissance-italians-1450-1630 which make me think that if the medieval Italians could have such strange beliefs about Africa and its inhabitants, there couldn't've been very many actual Africans/blacks among them; and if that's true about Italy, which is right there above Africa, what about England, a continent away (so to speak)?