The UK is a member of the European Council, which means it is subject to the jurisdiction of the European Court for Human Rights.
There's some talk of leaving the European Council because Brexit, although it's worth noting the European Council was Britain's idea and top British minds drafted the European Convention of Human Rights.
The ECHR declared their case inadmissible and said they'd only intervene on an exceptional basis when there was a real risk of irreversible harm to someone (so basically "he's dead already, listen to what everyone told you".)
Separately the UK chose to sign up to an optional protocol in the UN on the rights of disabled people so the UN asked for a delay to consider the case, but because for whatever reason the UK never integrated that protocol into law the Court of Appeal were able to go "LOL no".