An email acknowledgement of the order with a statement to the effect a contract is entered only on despatch of goods would be fine, almost all the large companies do this to protect themselves against mispricing errors. In the past it used to be on monies being accepted, but in mispricing cases by the time a large retailer identified a problem they might have lost thousands of £. I was banned by Orange from buying handsets years ago, they lowered a £389 phone on pay as you go to £34 in the sale, instead of £340, I bought 20 for cash and insisted on the contract being honoured. They did so, but banned any future purchases from myself. That was approx 20 years ago.