Need occasional childcare for 3 hours after school

I'm looking for a reliable babysitter to help with occasional after-school care. Typically I need someone for about 3 hours, starting right after school lets out, to supervise homework, prepare a light snack, and play with the kids. We have a calm routine, and the kids are 6 and 9 years old. Preference is for someone patient, DBS checked, and able to engage them with a mix of crafts and outdoor activity when the weather allows. Flexibility on start times within a 15-30 minute window is appreciated. Location is central London, easy transit access, and we typically require care on weekdays after school or on occasional weekends.