Make no mistake here.
Whether you have settled the tax or not, makes little or no difference (at the moment) to whether the loan is properly repayable or not.
A loan within Part 7A of the tax act (ITEPA) which is written off, will create a tax charge.
Do not go down the 12% route unless you have settled AND have written confirmation from HMRC that they will not tax the write off.
Given current lead times, that might take 6 to 10 weeks.