I have had an enquiry for a child to start in November she will be a school pick up 3days a weeks my fees will be £27 a week do I charge the parent now a retainer or take a deposit then take off first months bills? Thanks in advance xx

Personally for that amount I would take a four weeks fees Deposit when they sign the Contract.

I do not return Deposits until the end of the Contract, I hold it to cover the Notice period at the end. This then means I can mark on my Contract that childcare will stop if payment is more than five days late and know I will not be out of pocket because I still have 3 weeks fees in hand.
It is also non refundable if the parents choose not to take up the place.