The Sale of Goods Act does state that goods must be as described. There's obviously been an error here. However I would tend to say it's more a breach of contract issue than an "as described" issue as there has been a clear mistake and an entirely different product has been ordered. It's been picked up before delivery though, which proves a slight complication - time of delivery is not automatically a condition of the contract under the Sale of Goods Act and this basically means that lengthy delivery time on its own is not a reason to hold the company in breach of contract and claim a full refund.
If I were you I would be tempted to write the retailer a letter explaining that the order has been incorrectly placed and therefore the goods that are being made are not the ones you have a contract for. Inform them that you have already been waiting a long time and therefore you are giving them [reasonable date, but not 12 weeks] by which to supply the correct product or you will hold them in breach of contract and claim a full refund.
Consumer Direct (who aren't Trading Standards, but are funded by the OFT) will be able to advise you on the steps to take, but it won't be an issue that Trading Standards would be able to help with.