The entire series was released on Laserdisc in Japan circa 1991. The discs boast English and Japanese audio tracks. No idea if they sound better than what else is out there though.
http://www.lddb.com/laserdisc/11594/BELL-455/Captain-Scarlet-and-the-Mysterons-I:-Series
I’m guessing (from gleaning over this review of Bandai Emotions UFO set: https://ufoseries.com/videos/ldReview3.html ) that they probably sourced all the English tracks from the film prints they had - although there seems to be few impressions of the Captain Scarlet laserdiscs specifically, let alone whether they sound better than the alternatives.
Only one way to way to find out I suppose but GOD they’re like £100 a set! 😦