I think it depends very much on the persons mindset; that is to say, what they themselves perceive to be good or bad.
Some people will say the poly-technical universities are bad because their not as prestigious, less funded, etc.
But I far from think the ex-poly's are bad. I have some friends who go to Caledonian university, and even Strathclyde (which by the way used to be a technical college and nobody I know thinks that university is bad, by any means.)
Also, if you graduate from poly-technical university (undergraduate), then you could apply for postgraduate studies at a more renowned Russel Group university.
It's all mindset I think, "bad" is what you make it.