Ultimately, it boils down to the volume of orders you secure – both military and civilian.
This is where life gets.....interesting.
Critical node is HEU facility, which currently the UK lacks. Though studies have been done I understand on establishment of a new facility. Much pearl clutching and hand wringing over 'treaties' and costs.
Production run would be massively eased by becoming supplier of 'dual key' weapons to European NATO in place of US. We could be talking many hundreds of warheads here and a steady flow of sustainment work. With the option of rolling upgrades.
Which has the added benefit of being an much more upfront and explicit arrangement for everyone involved.
The US weapons were never 'free', just the 'price' wasn't a simple matter of money. But with us it would be straightforwardly a contractual arrangement.
Actually a win-win-win here.
Europe gets greater assurance over nuclear umbrella.
US gets to withdraw their nukes and save billions.
Russia gets an upfront process that's restraining certain European states.....how shall I put this nicely?....ambitions.
If Germany, Netherlands, Norway, Italy, Sweden, Romania and Poland stump up the cash, UK and France can provide.
As it is UK-French sharing of facilities is increasing. Current events could be the trigger for acceleration and deepening of that relationship.