Hello, this is Jim and I’m a dual-qualified lawyer (UK & Republic of Ireland) happy to help you today.
The nursery/childminder should not be charging you for a service which they cannot offer. The essential term to the contract you have with them is that you pay them - and in return they provide childcare services.
If one of these essential terms is not able to be carried out, in this case due to an external event being the pandemic, you can refuse payment. The term here is "force majeure", or an "act of God" clause - meaning that if performance of the contract is impossible then the parties can agree to suspend their obligations - for the duration of the force majeure, or in this case, for as long as the service cannot be carried out due to the lock down.
Therefore, you would be within your rights to withhold payment until the nursery is in a position to resume their own contractual obligations and provide the service.
If they dispute this, threaten them with a report to Trading Standards (tel: 03454 040506). If they threaten anything else such as court proceedings (which would be unlikely, especially as most court cases are not now going ahead) then come back to me - I can assist with any response to the claim.
I hope this helps? If you would kindly leave me a 5 star rating (at the top of your screen), the question will stay open and any follow up questions are welcomed.