Right. Two problems now, the Army isn't a school. You don't just "exchange" army. You can sometimes work with others in terms of two squads working together but you don't actually swap over.

Second, to join the British military you have to be a citizen for at least... ten years I believe. Seriously if you are dead set on Dutch just mention having a dual nationality, and you simply joined up in the British military OR.. You were in the Dutch army, did your term and then enrolled in the british army as an officer.