Well shy don’t you try it in with them.
If they don’t inform you of error before hand then this applies, which they sent me when cancelling my gels due too “pricing error”
When placing an order on Halfords.com, customers accept our terms and conditions of sale. Section 2.2 of the terms and conditions show:
“The Order shall only be deemed accepted by Halfords when you have paid for the goods, monies received by Halfords and the goods have been dispatched. Any email, order confirmation or other electronic acknowledgement by us of receipt of an order does not constitute legal acceptance by Halfords of your order.”
Demand the goods you ordered.