I have a family who are looking for after school/school hols, 5 days a week from Sept. They are coming to see my shortly but on just speaking to another local childminder she says she doesn't charge a retainer, or just £50 max to hold the place. So I;m now thinking of what to offer them to secure the place. The monthly fee comes out at £300 per month.

any advice appreciated

If it was the last space we had then I would say to hold the place they would need to pay a retainer of upto half fees. If I have more than one space I ma more flexible
Iv not yet had any parent willing to pay it though

As its only a couple of months it might better to charge a deposit which will be taken off their invoice (I usually say after the settling in period has gone so second month) I usualy charge £150 and this is non returnable if they dont take the place or terminate the contract within the settling in period