He only solicited 2. The extra 2 are unsolicited no?
No, thats outside the terms of unsolicited goods. Goods sent in error are not unsolicited goods.
The concept of unsolicited goods were goods sent to somebody, along with an invoice for them, with the intent that they would receive them, begin using them and be forced to pay for them. The law ensures that if this takes place, you may keep them as a gift.
Mistakes are not unsolicited goods, they are mistakes.
The Theft Act makes it pretty clear that coming into the posession of somebody elses goods as a result of a mistake does not mean that retaining them isn't theft.
I would notify them by Recorded Delivery letter that you have posession of goods received as a result of a mistake by them. Offer them the opportunity to arrange a courier to collect them at your convenience. Most places will consider the hassle not worth the bother and you'll then be able to safely keep them, IMHO.
Lets follow it through the Theft Act.
What is theft? Well..
A person is guilty of theft if he dishonestly appropriates property belonging to another with the intention of permanently depriving the other of it; and “thief” and “steal” shall be construed accordingly.
So, you need to dishonestly appropriate.
So what ISNT dishonest? This..
A person’s appropriation of property belonging to another is not to be regarded as dishonest—.
(a)if he appropriates the property in the belief that he has in law the right to deprive the other of it, on behalf of himself or of a third person; or.
(b)if he appropriates the property in the belief that he would have the other’s consent if the other knew of the appropriation and the circumstances of it; or.
(c)(except where the property came to him as trustee or personal representative) if he appropriates the property in the belief that the person to whom the property belongs cannot be discovered by taking reasonable steps.
a) doesn't apply because they are not unsolicited goods, therefore he is not entitled to keep them by law. I guess you could argue that until he finds this out it isn't technically theft yet as he 'beleives' it is covered by law. But he now knows its not, so that doesnt apply.
b) Doesn't apply because the owner would not consent to the retention of the goods if they knew.
c) N/A
And appropriates?
Any assumption by a person of the rights of an owner amounts to an appropriation, and this includes, where he has come by the property (innocently or not) without stealing it, any later assumption of a right to it by keeping or dealing with it as owner
So, it meets the criteria of dishonestly appropriated, therefore retaining them without making the effort to return them is theft.