IMHO, Dixons' "Galaxy" (and later "Prinzflex") brand lenses were almost universally "acceptable" at best, and abysmal in many cases - certainly not worth much nowadays in terms of either financial value or, more importantly, "image quality" (whatever you consider that means!).
The only lens of those brands that I ever bought was a Prinzflex M42 2X TC in 1970 (for about £7 on 6-months' "interest-free" credit = just over £1 a month - but then I was only earning about £85/month
gross at the time as I was a graduate apprentice and so it was "quite a lot"
). Never again, as I was "not much impressed".