OK. I have only the vaguest notion of Cats and Traps but 2 Billion quid to retrofit as a system, really!!
Let us say I have the UK's checkbook, surely if we purchased the hydraulic bits needed for the Traps of the USA I would budget that at £10 million per carrier.
Now the steam generation system is way more complex, but Older UK non-nuclear carriers had steam catapults, let us say £150 million to fit this.
Could it be that simple, what have I missed?