Your questions are sort-of answered in the article. 3300 die each year of cervical cancer in the uk. So at 0% it saves 3300 lives per year. However the vaccination is fairly new so they have to wait longer to see if it applies 20-years, 30-years, etc later. I assume it would though.
Parent's question isn't answered in the article - no figure is given for how many deaths under 30 there are as a baseline.
From the article:
“We estimate that since its introduction [in 2008], HPV vaccination has prevented nearly 200 young women from dying from cervical cancer in England.”
This is an estimate of 200 total of any age total across 18 years. The article doesn't say 3300 die each year, 3300 are diagnosed each year.