Of the 5% of people who do have dysplasia after first having a lletz and 1 year later a cone biopsy, how many will develop cervical cancer?

Depends on staging: If the procedures were done for CIN III also known as severe dysplasia or carcinoma in situ and it was eradicated TOTALLY by Pathology report then there are few recurrences of note. If the Lletz or LEEP procedure extended beyond the borders on the Pathology report or was invasive carcinoma then statistics are different entirely.