Mandy Mountjoy is the creation of porn starlet Heqther Chittenden. Heather was an average boob sized (C cup) pornstar from Surrey, England most famous for being in the Ben Dover movies in the early to mid 1990's. Around 1997, Mandy pasted some crazy prosthetic boobs on, dyed her hair black and made a couple of movies as Mandy Mountjoy. Zena Fulsom
and her 'sister' Cindy Fulsom
also used the same prosthetic stunt around the same time frame. Judging by the size, it look like 'Mandy' borrowed the pair of boobs the Fulsom's used.
Rumour has it that Mandy was pushed out of the business by the starlets who had their breasts surgically enhanced.