Not my specialist subject but I don't believe you are entitled to a refund. Equally the supplier is not entitled to dispose of the item ordered and paid for by you without giving you written notice of you requirement to collect.
If this is so, you would seem to be entitled to the goods but not a refund.
I don't know where you stand legally, but morally they would have incurred the cost of ordering / setting up your particular key which you then didn't collect. Don't they have a right to be paid for fulfilling their part of the bargain ?
You don’t have to refund a customer if they: no longer want an item (eg because it’s the wrong size or colour) unless they bought it without seeing it.
Copy and pasted from the above link.
Looks to me like it's up to the Op to collect the goods or arrange delivery but not entitled to a refund.
I think Buildsersmate is absolutely right.
What would you have done if, last February, you'd advertised something for sale, someone had bought and paid for it and said they'd collect it later and then never turned up again? I suspect you would have thrown it away by now (depending on its value).
Why not go along and pick up the replacement key.... you might lose the original again, and anyway if you go to sell, the new buyer would be delighted to get a second key as often more than one in the house needs a key to the car when out shopping etc.....
Under the Sale of Goods Act the only way you can get a refund on goods is if they are faulty, don't match the description or not fit for purpose.
Even if you told the seller you no longer wanted the key a day after it was ready you had no grounds to reject it and get a refund. The key was made specifically for you and cannot be resold.
When you ordered the key and paid for it you entered a binding contract.