My view is that when a parent uses the services of a Childminder, they are paying for a Childcare Place. DfES certainly talk about number of Childcare Places when referring to daycare provision.
Therefore if the Childcare Place is available and the parent chooses not to use it - then I feel the parent should still pay. If the Childcare Place is not available, then I do not feel there should be a charge.
However, there may be circumstances where a Childcare Place is kept available for a parent to use in the future, and to avoid losing that Childcare Place, the parent pays a retainer fee.
Thus:
If you are open on a bank holiday - then charge.
If you go away on your family holiday - then don't charge.
If the child is sick - then charge.
How you market your childcare service however starts to affect things - as parents will shop around childcare providers and will compare prices. Some parents will work out the Total Cost, where as others will only look at the Hourly Rate. This is of course just my view - Are there any parents who are currently looking for childcare reading this? If so... do you compare Hourly Rate, or overall Cost?
To achieve a lower Hourly Rate, you may need to charge fees for periods when you are closed, in order that your service is viable.
There are pros and cons to the various methods of charging. Some parents like to pay the same every month for childcare for example... where as others prefer a pay-as-you-go type method.
Ditzyprincess as a newbie Childminder, I would suggest that you research your local market, find out what other daycare providers are charging, and then decide how your service will best fit into the local mix.