Seller says item is out of stock and will refund, but does not.

[tbmod]

I ordered something today, the seller replied almost instantly that the item is out of stock and he will refund., but no refund has been forthcoming. I waited several hours and messaged him asking what was happening but have received no reply.

I need to reorder from another supplier, but would like the refund first, to avoid currency conversions. How long is a reasonable time to wait ? 

If he doesn't refund, how do I contact ebay in this situation, requesting a refund, without waiting till the end of the delivery period ?