That is hard to tell, Warwick. But even if the CDIs are never cancelled, I am sure you know this by now, holding CDIs is not the same as holding shares. In fact it is a big disadvantage as stated in the Scheme Booklet page 49:
• holders of CDIs will not be directly entitled to certain other rights conferred on holders of NewCo Shares, including the right to apply to a Bailiwick of Jersey court for an order on the grounds that the affairs of NewCo are being conducted in a manner which is unfairly prejudicial to the interests of NewCo Shareholders; and the right to apply to the Jersey Financial Services Commission (JFSC) to have an inspector appointed to investigate the affairs of NewCo. (my emphasis)
As a holder of the NewCo CDIs, you will not be directly entitled to certain other rights conferred on holders of NewCo Shares.
Just think about that for a moment. I am sure you will know what to vote to this proposed scheme.