I did over hear a conversation why the UK has no FCC available to purchase at the moment but as it's hearsay, I have no idea if it's true or not. Seemed plausible and it also indicated this isn't a permanent arrangement but it's no big deal.
With judicious planning, and risk, obviously, if you're pretty sure you'll be booking in the future, for a very small deposit, you get the perks offered for an onboard booking and at the moment, that booking can be transferred once, to a cruise of equal or greater value, with no penalty as long as time elements are observed.
A bit like purchasing FCCs but with the small deposit as an outlay rather than whatever the cost is now.
As I said, a bit of planning with future itineraries is required but the outcome is the same if the planning fits and VIP, the one time no penalty transfer can be undertaken.