I don't think there is such thing as worst university.
It comes from subjective opinion.
Only you can determine what the worst university is.
Top 10's can't determine what is worst university is for you.
You can only know if you have been in all universities in the UK, which is highly unlikely.
For me there isn't a worst University.
I however think that University of Manchester is better than Manchester Metropolitan University. UoM has more subjects than MMU. I also think that UoM has better environment for me. I am more comfortable with the UoM environment. UoM is more strategic, deciding and disciplined, whereas MMU is more spontaneous, browsing and whimsical. Which is why UoM attracts me and MMU does not.
I also think University of Salford is better than MMU but I am not appreciated to the organisation of UoS as I am with UoM.