Two possible explanations.
It could be a 'brushing scam' - google for details.
Sometimes overseas sellers provide UK addresses (not their own) for returns so they don't have to pay for tracked postage back to China or wherever.
If you haven't ordered anything, and you are definitely not waiting for anything to arrive from an Ebay seller, I would bin it and forget about it.
Another scam is where sellers post a cheap little item instead of the larger, more expensive item you have bought.
When you try to claim non-delivery, the seller has tracking proving that a parcel was delivered to you.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)