It seems to me that the transfer of the costs of the Trident nuclear system to the Department of Defence (Future of Trident in doubt as ministers row over budget | Ekklesia) is right and offers new hope.
Unless the Ministry of Defence bears the cost of everything related to defence/military expenditure it cannot be expected to make the decisions based on cost effectiveness. If they do not pay for Trident then it should be no wonder they want it as it will appear to be fantastically cost effective.
By putting the costs into the MOD it will have to be justified as cost effective against the alternatives. Personally I am confident that in any fair comparison the full costs of Trident will not be cost effective and so on those grounds alone it should be abandoned.
My own view is of course that it does not matter at all if Trident is cost effective, it should still be abandoned and all our Nuclear weapons decommissioned immediately. That to be followed as soon as possible by ideally a complete demilitarisation of the UK.
Step one in all this should be immediate progress on banning all arms sales to anyone anywhere by any British company, any British passport holder and anyone on British soil. That will then need to be extended to include all forms of transport for arms and all supporting equipment, good and services.