I've sent two items to a buyer in a combined package, paid postage via one of the listings, but it will not allow me to mark the second item as dispatched ?
If you generate the original prepaid label it will mark the item as dispatched. Then if you paid for it you can cancel it here: https://www.ebay.co.uk/claims/simple-delivery/refund/seller Or if the buyer paid for it it will be refunded to them automatically in 30 days.