So whilst moving between github organisations - which is relatively straight forward, I also had to move some from Atlassian Stash unfortunately there's not as simple a method to do this, but a good way of mirroring between two repos is as follows:

$ git clone https://donor_repo/example1 --bare
$ git remote set-url --push origin https://destination_repo/example2.git
$ git fetch -p origin && git push --mirror

Simples.