Leaving on your own terms means appearing before an officer first. The officer checks that you can afford the trip to a country that will let you in, and that you genuinely intend to complete the departure steps. You then name where you want to go, and the officer has to approve that choice unless you are a danger to the public, a fugitive from justice, or trying to evade justice somewhere.
(1)A foreign national who wants to voluntarily comply with a removal order must appear before an officer who shall determine if (a)the foreign national has sufficient means to effect their departure to a country that they will be authorized to enter; and (b)the foreign national intends to voluntarily comply with the requirements set out in paragraphs 240(1)(a) to (c) and will be able to act on that intention.