The sequel was indeed called SHOCK TREATMENT, about TV show where poor Brad was locked up as a prize for Janet and Betty and Ralph( who were martried in RHPS ) were cast with Ruby Wax.
Sequel to Rocky Horror with son of Frank, Tru, includes Magenta, Riff, Son of Frank, Brad n Janet and a time machine woo-hoo and some Cryogenicaly frozen folk who were chucked of ship at same time as Brad, Janet n Dr Scott, hmmmmm coool