Q:

Employer has offered a promotion and training, but I am planning on leaving in 8 months - should I take?

I have been working at this company for almost a year now, and I have been offered a promotion and training to go with. My old job here will be cut, that is part of the reason why I have been offered this one, so they can keep me on. This job was created for me. This means I have to take it or leave. 
Meanwhile, I have been studying for university entry into a completely different field (engineering) than the one I have been offered a route into (HR). I have passed all exams well enough to have secured a fully-funded scholarship including living expenses starting from September. 
My dilemma is that I will be leaving in September to take up full-time study, but I feel for the people that put in so much work to allow me to stay. Should I open up about my plans? Should I allow things to proceed, hide my plans, and hand in my notice when the time comes?
I am afraid of becoming jobless for the upcoming 8 months, but I don't want to screw these people over - training is expensive!
What would be the most ethical course of action here?
EDIT:
Thank you for your answers. My question is not just a case of 'should I tell my employer that I am leaving?'. It is more like : 'Should I undertake a new role and training regardless of the fact that I will leave?'. Sorry if that was not clear. This question was not a repeat of others. 

A:

Don't tell them about your plans for school until you have to. Your current contract or new contract will explain your notice period.

I have passed all exams well enough to have secured a fully-funded
  scholarship including living expenses starting from September.

I have seen schools renege on a scholarship commitment. It is rare but it does happen. Therefore there is a small chance your plans will change.

This job was created for me. This means I have to take it or leave.

There are two important points here. You know you almost lost your job, and they know that you know.
Management knows that the smart employee sees this as a sign that they need to start thinking about other jobs. The fact that they made this opportunity available to you is a good sign, but it doesn't remove all risk. They will not be surprised if some employees in this situation decide to switch companies, employees  need to go where they see the best opportunity and security.
From your comments:

The training is ongoing under the regional HR manager as an
  apprenticeship - while I am training I will still be undertaking full
  HR functionality as the sole representative at this particular branch.
  I will have to undertake a self-paced course online as well

There is a chance you might not like the regional HR manager, or you might not like the job, or could fail the training. So unless they are locking you into paying for the training class, or there is some other obligation to payback the company if you don't stay for X years, the risk is on them.

