Sorry to hear this, but in all fairness to those sellers they agreed to the return and followed the correct process and will have waited a considerable amount of time before those return cases timed out.
Trying to issue a chargeback via your card provider will be extremely unfair on them as they'll be hit with a £16 admin fee, and as you've already had eBay return cases close when the ball was firmly in your court it could backfire on you.
Perhaps list them yourself?