What are the advantages/disadvantages of LLC comparing with LLP in UK?
Where should I start learning about doing business using LLC? is there any online guidence how to choose the right state, annual reports, audits, some e-learning materials and so on ? (like HMRC gov resources)
Since our service covers only entity registrations in the US I would not be in a position to give you advise on UK LLP.
Generally speaking, if you do business both in Europe and in the US you might want to register in both. As far as states go I recommend you to consider either Delaware or Wyoming.
As far as LLC goes you are welcome to start your research here.