There is nothing you can do as a buyer unless the item was under the value of £25 then leaving feedback could release the payout sooner, unless this is a new or returning seller , then their payout can held for longer, 30 days.
As said, nothing you can do, there is nothing to mark an item received, the seller has to have tracking to show delivery, or payout is held for 14 days, or longer.
@angecou_22