Having skimmed through the 45 pages of 'Judicial Pensions: Proposed response to McCloud Consultation'... there is a nugget of good news "it is acknowledged that it will be necessary to pay interest where MoJ owes money to the member or member’s estate or dependants". Hopefully this is the full statutory 8% as the debt is a result of a law being broken.
If the AFPS goes along the same lines as the MoJ, it looks as though options will not be available for some time, unless you retired after AFPS 15 came into being in which case it would be earlier...