I didn't know ebay allowed you to cancel a partially refunded transaction. I usually just don't bother getting FVF back with partially refunded transactions, Will look closer next time.

That was actually the first time I requested a cancellation after a refund - the few other times I've refunded it's been my fault or a faulty product, and I didn't bother those times. There's been a few threads over time where buyers have queried why a seller would send them a request to cancel a transaction a few weeks after receiving the item and leaving FB etc, so it seems it can be done without even issuing a cent in refund. (Presuming the purchases were paid for with PayPal, anyway, and that the payment status remains unchanged).