Don, you are certainly right to say that there must be more than these 17 cases.
That is just the actual convictions, in this limited area.

This good lady has worked with 400 families (FOUR HUNDRED!) of young girl victims since 2002, and she believed even that is just the tip of an iceberg.

This from the Guardian.
Hilary Willmer, of the Coalition for the Removal of Pimping, said that since 2002 her group had supported 400 families where girls were the victims of grooming and sex abuse by mainly Pakistani men. "The vast majority are white families and the perpetrators are Pakistani Asians. We think this is the tip of the iceberg." But she cautioned against treating the matter as a race crime. "It's a criminal thing."