Just "Attention" alone is also possible in written BE, too. If I was reading it out, though, I would say "for the attention of", as "Attention Mr Jones" would sound like someone on a tannoy system.
Ina, did you notice the preposition? The question is whether "to" or "for" is correct at the start. In BE it's definitely "for", see the dictionary entry in #0 and the Google hits here. Maybe someone can find a dictionary with the "to" version in AE? The quotes and Google hits above do make it look as if both are possible in the US, but it would be good to have an official source too. (What is the logic of "to" here? I don't understand how you can send someone something to someone's attention...)
For "zu Händen von", Hamblock/Wessels Großwörterbuch Wirtschaftsenglisch has "attention, for the attention of, care of, c/o". Dietl/Lorenz has "care of, for the attention of, attention".