hulahoop,
"The £1.4 Bn" is an utterly meaningless figure dreamt up by the half wits who the FT employ - who have not the first idea when it comes to defence subjects, and who are spectacularly clueless even by the standards of 'Fleet Street'.
I can be confident about that, because the cost of Tranche 3 is not known, is still being negotiated, and isn't yet set.
If Industry are to be believed, then one would expect the unit production price to be marginally lower that the unit production price of Tranche 2, which was €55.08 m (equivalent to £37 m on the day the contract was signed).
You might therefore expect the UK share of the T3 production contract to come in at somewhere over €2 Bn.