So yh, just that. Had a few issues this morning with them not able to take payment. So I rang up to try and sort it but got nowhere. I rang a different number and got put through to a manager, the manager took my car details and the payment went through, that's what he said anyway and said my shopping would be delivered.
I remember checking the bank due to the confusion so I know exactly how much I had in there. Shopping has long been delivered and I've just looked at my bank and the money is still in there. 
Would I be unreasonable to put the money into another account and say nothing? If they ask for the money at a later date I will offer to pay in instalments but i couldn't do it all up front especially as it wasn't my error.
What do you think I should do?