In that case I'd say that any warranty would be with said company. Just check what their terms were on the original ad.
Only certain companies would count eBay invoice as a proper receipt iirc, EVGA would if you were buying from the original owner for instance but they were always pretty savvy in that regard.
Yeah in their listing they specifically say no warranty but have yet to get back to me regarding some sort of invoice from Dell so i could claim from Dell direct if anything happened. The listing says this:
"This item is a customer return, the packaging has been opened and there may be damage to the internal and/or external packaging but the item has been fully tested upon return to us and is in full working order and the product/accessories considered to be in "as new" condition. The item may have non-permanent signs of handling, such as fingerprints, etc that are consistent with the product being inspected and tested.
Some internal packaging such as cable ties, bags or protective films/wrappings may be missing or damaged. Some paraphernalia such as quick-start guides or manuals may be missing, these are usually available to view/download on the manufacturer's product page.
All of our return items are sold WITHOUT warranty, any item that arrives in a non-working condition can be returned within 14 days of purchase.
We have multiple quantities of this item, you will not necessarily receive the item pictured in the listing but all are a similar condition of item/packaging.
Will be sent safely and securely, ships same day (if ordered before 2pm)/day after ordering Mon-Fri. Orders placed on a weekend or bank holiday will ship on the next working day.
Free UK Shipping. Don't hesitate to ask if you have any questions."