Hi,
I can't help with identifying your Grandmothers trade, though I have a feeling that a jennier is to do with spinning the thread.... but I really am not sure.
But from a book of old Nottingham street names I have , it suggests that Havelock St was off St Ann's Well Rd, and that road does still exist, it is not far from Huntingdon St, and runs up the side of St Mary's Rest Gardens.
My Great Grandmother worked at a lace factory on Weekday Cross, in the lace market, at the top off Low Pavement. I imagine that there were factories all over Nottingham.
Nottinghmam Library have very good large scale old Nottingham maps, worth a visit if you can.
Hope that helps!
Copperbeech5