One source...

This is indeed one of the best vampire films in the past twenty years.

That being said, having only one source of creation, a remote stone island off the coast of the UK, seems odd. The passing of bodily fluid from one vampire to it's victim maybe a bit too simple I suppose, but makes movie\folklore sense in that victims become vampires thus spreading like an infection (which is why tuberculosis was often blamed on vampires; one family ember got it and died and soon others in the same family got it and died).

Stephen King spoiler: In the short story sequel to Stephen King's "Salem's Lot" called "One For The Road", it is implied all of Salem's Lot has become a haven for vampires. One created a town full.

Here only those who know where the island is and can get to it can be transformed. Keeps the vamp population from getting out of hand, I guess!

Having a ritual of some sort to create or pro-create anywhere would have been better.