The real issue is with a satellite launcher is: what satellites do you want to launch?
One of the problems with any UK launcher was – what is it there to do? Okay, you can launch a few scientific satellites, but the proportion of the science budget that it would swallow up would be entirely disproportionate.
What other applications were there? Well, back in the 1960s, satellite communications were becoming almost a commercial proposition, providing your launcher can put a reasonable payload into geosynchronous orbit.
And none of those HTP launchers would have been able to do that.
Any other useful commercial applications in the 1960s?