I see you tagged estimated dates. Is it just that they delivered later than eBay estimated delivery times? Or that they didn't deliver at all? If it is eBay ETA, then ignore these! Many people have complained about them being unreliable at the moment.
If it is undelivered items, did you speak to your local Postie? Or raise a complaint each time with Royal Mail? Yes, it takes a bit of time, but is worth sorting if there is a problem with your parcel deliveries. Good luck!