Manchester isn`t great place for tourists,i have to say. quite small and dirty. i would recommend Science museum and shopping during the day and i think everyone can find right place for partying during the night. the thing i did not like the most was... bunch of drunken english teens(i like to party and i travel a lot,but english kids are just awful and the most annoying people i`ve seen!!)!
so my advise is... if you want to visit England,but can go to different place... just do it!!
cheers