Do you perhaps have any more information about the temporary layout of HMS Edinburgh (with single Phalanx fitted behind main gun), and the envisioned Type 42 Batch 3 with one Phalanx and two 4-cell SeaWolf launchers midships? There where some layouts available on secretprojects.co.uk, but they have been taken down. All I can find are some photos en information as stated below:
I don't have any information specifically for that planned refit.
It seems an odd place for a gun CIWS given the limited arcs of fire (plus the water and spray issues encountered). The problem was the lack of adequate top weight margins. Many of the Batch 1 and Batch 2 ships with Phalanx had to lose their torpedo tubes as compensation. I suspect that with the beam spaces earmarked for Sea Wolf the only place left for a Phalanx was on the bows, for example putting it atop the hangar was probably difficult due to topweight. The fire-control required for Sea Wolf would have been awkward to fit too, both for space and topweight. I have a feeling it was too ambitious.
As Erik says, these were austere ships and even the Batch 3s were not fully optimised (hence the visible hull reinforcement).