No.
You can choose it to be UK only, EU only, worldwide or any selection of countries you want.
Most of the Ebay listings I see are for sale only to UK. I think it would be difficult on Ebay UK to find a second hand PC being offered to anywhere but the UK, due to the cost of international delivery not making such a sale cost effective.
And like Keynes says you can offer any method of delivery you want, and you can specify pick up only.