If a buyer purchases a used item that doesn’t work, who pays for the labour to fix it?

[malaw4155]

Hi all. In a bind here: If a buyer purchases a used item, claimed as being in good working order, then affords the labour for fitting said item only to find it does not work as described- who pays for the labour? 
I’ve seen some allusion to seller responsibility (consumer rights act), but wanted to know if anyone has had a similar situation and what to do about it, specifically through eBay?  
Seller had said a refund will be made if the part is theirs (gave a fair load of abuse about fraudulent claims, police threats and general rage that I dared claim it was faulty) but of course to return the item it would require the part be removed from the car again, £400 further for labour. Mentioned this to the seller, including the specific page from the consumer rights act, and was ghosted. I did expect this, just wondering if anyone has some worthy advice?

[plum993]

A seller on ebay only has to pay a full refund when a case is opened by the buyer for item not as described within 30 days of the last estimated delivery date.

[tobiasd4]

To claim under ebay MBG, you have to return item within 30 days.

Seller has refund item cost and postage. 

Any claim for labour to fit and remove item is between you and seller, ebay won't get involved with that cost.

If it was UK business seller, contact citizens advice.