If I had paid on my Barclaycard, I would ring Barclaycard and tell them that the company I ordered goods from has not delivered them and I want a refund.
Whether I had or hadn't paid on Barclaycard, I would call Oxford and tell them that I am leaving the country in two days time and need the books before then. If they cannot absolutely guarantee that they will be delivered then, I would ask for a refund to be sent immediately.
Always best to put these things on credit card, helps with the refund as it is instant.
Then go spend your money with someone who is interested.
As far as I see it, Oxford have broken their contract with you and you have been reasonable and therefore it is totally reasonable of you to expect an immediate refund. Don't be fobbed off, ask to be put through to accounts dept if you are expecting a refund by cheque or talk to someone high up in the company.
Good luck.