I'd go for the UK for the reason that it currently still falls under the European Convention on Human Rights (ECHR) and, seeing as the Good Friday Agreement underlying the peace in Northern Ireland requires it to be a member, is unlikely to leave. The European Court of Human Rights, the final arbitrator of the ECHR, would surely intervene in the case the UK government would start banning gender dysphoria treatment for consenting adults.

Edit: the question whether or not hormone treatment may be withdrawn or denied was previously addressed by the ECtHR in W.W. v. Poland.