If you haven't received the collection code, and tracking shows as delivered, then you will need to contact eBay to request it. Use the following link to request a callback (best to do so first thing in the morning so that you get someone from the team in Ireland who are more knowledgeable and have greater authority):
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
8am to 10pm on weekdays and
9am to 6pm on weekends