Zero. UK terrorism stats show Islamist extremists behind most mass-casualty attacks since 2000 (7/7, Manchester Arena bombing, vehicle rammings prompting bollards, etc.). Far-right attacks exist but are rarer and less lethal overall.
On grooming: Major inquiries (Rotherham, Rochdale) found organised group-based CSE disproportionately involved Pakistani-heritage men targeting white British girls—not the reverse. The 250k figure is unsubstantiated; documented victims in those scandals number in the low thousands total.