I don't think you can do anything through Ebay as you no longer have the watch.
If it was expensive, it may be worth taking legal action as you reported it to the police but contact the seller first.
A quick 'google' shows that you have a right to a full refund from the seller but you will have to pursue this.
This is from Citizens Advice:
'Ask the seller for a refund as soon as you can.
The police will give you a crime reference number and property log number when you hand the item in. Show these to the seller as proof that you’ve handed the item in, along with your receipt or any other proof of purchase - for example, your bank statement.
You have the legal right to full refund from the seller. This applies even if it’s been a while since you bought the item and you’ve only just realised it’s stolen.'
"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)
