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If you'll forgive me @MoonRabbit, repatriating the British deterrent and its delivery system is doable. You do it by doing it in slices, exploring alternates, and keep it off the books (see the Chevaline project for an example: https://en.wikipedia.org/wiki/Chevaline ). All that is needed os the will of a competent government

Unfortunately I think that (for different reasons) Starmer, Badenoch and Farage don't fall into that category

You need:

(a) enriched uranium or plutonium

We have a civilian nuclear industry so we have the raw materials. We don't have HEU, currently. But this also isn't that technically complicted to achieve; you just need a bloody load of centrifuges, which can be relatively easily and cheaply acquired.

(b) to build a warhead

Nuclear warheads are not that complicated. The basics, unless you want to go the hydrogen bomb route, are terribly simple. Sphere of HEU. Shaped charges. With today's modern electronics, it really wouldn't be that complicated.

(c) a delivery system (i.e. a missile)

There's really no reason why Storm Shadow could not carry a nuclear warhead. It would only be a small one (it can carry a 450kg warhead), and there are clearly some engineering challenges involves. But ultimately Storm Shadow (like every cruise missile) is basically just a plane, and while it might look a little ungainly to stick a nuclear warhead in there, it could clearly be done.

(It's a lot easier to make a cruide missile nuclear capable than a ballastic one.)

If you have a plane-based deterrent, then you need to keep several in the air 24/7 (not the same ones: you rotate) because the time to get them in the air from the ground base is greater than the time it takes the Russians to nuke the ground base. SLBMs are preferred for a reason.