Had a duplicate postage refund to do & looks like Ebay have refunded part of the BPF as well :-

So the order total was £1.34 & BPF seems to have been reduced to 35p. (Ebay refund of 41p)
So looking at this logically it would be cheaper for buyers to buy items separately & get postage refunds - however when the seller refunds this will be immediate from available funds (or next available) while the funds for the order (including the payment for the refunded part) won't get released for a while !
(Ebay's I.T. really need to link payments & refunds to specific orders).