Since 2000 the regulations surrounding this type of occurrence have changed. Before 1st November 2000, the law stated that the company that sent out any unsolicited goods received before this date had to be notified. The sender was then responsible for collecting the items within 30 days. After six months the receivers would be able to claim the unsolicited goods as their own.
Essentially, because you have not ordered the goods, they could be viewed as unsolicited goods, which is where the changes to the above statement become relevant.
The Department for Business Enterprise and Regulatory Reform (BERR) states that under the Unsolicited Goods and Services Act 1971, (as amended) it is an offence to demand payment for goods known to be unsolicited.
This basically means that if you have received items without previously requesting them you cannot be billed for the items. You did not choose to enter into a contract with the seller to receive or pay for this item. Because you had actually ordered goods from the company and they sent you extra items in error, you have a duty to return them as they're not strictly unsolicited.
You have no obligation to pay for return.
As the receiver, you have no obligation to pay for the return costs of the goods if they are unwanted. If the company does demand payment for return costs, report them to your local Trading Standards Department.
Inform the company of the mistake, (you have) and wait to hear back from them (again you have). They should send you details of how to return the item with minimal inconvenience and no cost.
As it stands you will have to make every effort to return the item and at least they have given you 3 months to do so. It must be possible for you to do this without incurring any financial outlay, apart from your time of course.
Just remember, it is an offence to demand payment for goods known to be unsolicited!
