The first sentence sounds like an American talking, because the speaker leaves out the word "that".... I hope that I have been of some help, definitely sounds better. The second sentence is also missing the word "that" after hope. This, in my opinion, is a mistake to speak or write this way. It is very, very common in English to express our hopes by saying: I hope that you Mother feels better soon, or, I hope that tomorrow's test isn't too hard. Another was to phrase this second question is: I hope that I have been of some help. To end the sentence with "to you" is redundant because your are obviously thanking the person right in front of you.

I think your second sentence is natural, the first is not clear about referent person.