Fireshadow is intended to operate at greater ranges than artillery, & be more precise. It also has scope to be used where long-range precision artillery won't be present, e.g. from fairly small ships.
FASGW(L) is already tested & in production, as LMM. It should be cheaper than Starstreak, & the current order absorbs part of a Starstreak order, the missiles being completed as LMM. We get to drop the expensive part of the Starstreak, & substitute the cheaper LMM parts.
SPEAR capability 2 is, as I understand it, an updated DMB. At the rate we're using up Brimstones, we'll either have to buy more or buy something else before very long, so why not just apply whatever technology updates have been developed since it was first thought of, & carry on?
Spear capability 3 could be a 100 kg class bomb with a wing kit, or a version of FASGW(H), or something else.
AFAIK it's still in the assessment phase. The emphasis is supposed to be, as with the others, on not re-inventing the wheel.
I don't see the point of phasing out Storm Shadow. We already have a large stock. Why scrap them?
AFAIK the plan is to upgrade the current stock, not buy large additional numbers.
The Norwegian NSM & its developments can't replace it. The total missile weight is the same as the Storm Shadow warhead, & the range is far less. It can't do the job. Don't get me wrong: I think NSM looks like a fine missile. But it's for a different role than Storm Shadow.