Company Tax and Visa Advise Help

My UK staffing company has been asked to send four uk engineers to Taiwan for two years to work on a clients site. I need some basic advice on how to manage the work visa issue and if we as a company will need to register there?

  1. To keep it simple, is it easier for the Taiwan client to employ these people or for us to register in Taiwan and to manage the process remotely?
  2. Is there any tax advantages to the personnel if they are employed via the UK or via Taiwan or is the rate of tax the same regardless.
  3. If the the expats are employed via the Taiwan client company can they, and do they need to, still pay into the uk n.i. system ?

Basically, we would prefer to hand the liability over to the local company but need to know if it makes any difference to the salary/ earnings of the expats.

Thanks all,

Jocko