No, Seacat 2 predates the work on Confessor/PX.430 by several years, though I suppose it could be argued that it was an influencing concept.
I have always been surprised that the Admiralty showed no interest in Seacat 2, especially given the early date of its conception, shortly before Seacat was being widely deployed on ships as they came in for refit or new-build ships finished completion. I suspect at the time Seacat was available and thought adequate as a 40mm Bofors replacement as a close-in self-defence missile despite its subsonic speed and visual-guidance. This is odd given that as early as 1956 work on projects like Orange Nell had shown that only supersonic missiles with radar guidance had any chance of success of shooting down missiles, but the emphasis switched to tackling the bomber before it released its stand-off missile.
By the time Seacat 2 might have been ready for production (mid-60s), the Navy had reverted back to the supersonic 'goalkeeper' missile that became Confessor/PX.430 that they hoped would enter service in the early 1970s to replace Seacat, but they seem prepared to wait for the ideal system they wanted. Doubtless had their been strong official interest, Shorts would soon have been knocking on the Ministry of Aviation's door demanding R&D money.
As we know now, Seawolf was a surprisingly bulkier system than Seacat and could not be fitted as a direct replacement and Seacat soldiered on far past its prime. In hindsight, if the Seacat 2 really had been able to use the same launcher and most of the similar equipment (I suspect some magazine changes would have been required), then it would have been a great upgrade not only for the Royal Navy but for export users too. Perhaps even a competitor to Sea Sparrow.
