Im not too sure if this will help, but  i asked a local girl (who babysits alot) how much she charges and she said

£20 for a few hours in the day,
£20 and a take away if she was to start or if she'd be babysitting at 6
£35 if it was sunday or after 8pm

but i also found an ad in my local shop window and the person wanted £4.50 an hour,£7.50 after 7pm.

I dont know if this will help, you or not but at least its something :-)

best of luck with babysitting.