Which brings us to another point.
It was clear in the late 1940s that SAMs were feasible and that there would be different requirements from the different services. It strikes me that a more logical approach might be look at what such missiles had in common, such as the guidance system, and standardise on that. Instead, we had three different missiles being developed all using entirely different techniques.
It is the sort of thing that the Ministry of Supply should have grasped from the outset, but then we all know what we think of the MoS. That the DRPC didn't press for more commonality is more surprising.
However, it is easier for us to sit here sixty years later and say, 'I wouldn't have done it that way!'
Bloodhound and Thunderbird were probably as good as other contemporary systems. Seaslug, as you say, was marginally successful.
Combined response:
Absolutely, both Bloodhound and Thunderbird were technically successful and achieved reasonable foreign interest- both could be seen as successful programmes- in stark contrast to other UK missile efforts. I agree entirely that it seems odd that greater standardisation was not pursued.
In late 1940-early50s, it's not obvious what will prove to be the successful design path forward. I mean, who would think that we're still using AIM9s and Standard Missiles in 2024?
So the UK in the interests of making the capabilities at home, has to develop
all the different paths. Liquid fuel rockets, solid fuel rockets, ramjets, beam rider guidance, SARH, ARH, TVM, IR, TV, all the different warheads, proximity fuzes...
At the very least, all the propulsion needs to be developed to either flying prototypes or someone saying "like hell are you putting Red Fuming Nitric Acid on my ships!" or equivalent.
Guidance needs someone to be able to say "Okay, we can do beam riding but that only works for point defenses, we need better guidance for crossing targets," and "you can't stick ARH in an 8-inch missile diameter and have it practically useful, so we're going to drop the idea for now."
et sim for warheads and fuzes.
And there's just no way around that problem. You gotta spend a crapton of money and some of it WILL be down dead ends (at least by 1950s tech).
Now, as to bolting an IR seeker onto a Bloodhound or whatever, that's a different discussion.