This is an unusually complicated and tricky situation. It would help if you let us have more information, for example when and how did you pay for this watch? When was it delivered and when did you open this case - which I trust was a money back guarantee case? Have you now escalated it for eBay to step in.
It isn't clear how the seller could have deleted his account. eBay does not allow users to close accounts whilst still within the time limits for possible money back guarantee claims. If it's already been closed only eBay could have done this.
I'm not sure how the money back guarantee now works if the seller is no longer a member. You may need to speak with eBay customer support.
As the seller is abroad, eBay's system of sending prepaid return labels doesn't apply. An eBay rep once told us that custmer support can still insist on the seller arranging the return. Don't count on it.
It will be up to you to reclaim your import duties from HMRC. Again, I'm not sure how this works if the seller is no longer a member as HMRC would normally require evidence that it has been returned out of the contry.
If you can't get a resolution through eBay your best hope is to approach your credit or debit card company for advice, if that's how you paid. They may be able to issue a chargeback.
Thre will obviously be no prospect of taking the seller to court as you imported it from abroad.
Good luck, I fear you may have quite a problem on your hands.
