This order was placed via the vendor's own website using MasterCard rather than on eBay.
An update -
When I started this thread I quickly reached the conclusion that I was not going to get anywhere with this vendor and started a dispute process with Mastercard to recover my funds. I also emailed the vendor to let him know that I was doing this.
I wasn't completely surprised to receive an email from him (my first, except for the autoconfirm of the order) that same day. It was a reply to one of my previous queries sent about ten days previously. He claims not to have received the one detailing my actions with Mastercard.
His version of events is as follows -
He is running a bit behind as he has been in a car accident and currently has a broken hand.
There was a problem with my order; one of the items has had to be backordered from a new supplier (Note - his website showed all the items I ordered as being in stock at that time)
He sent me a previous email informing me of this (Note - I received no such email)
Upon receiving this I sent him a very strongly-worded email demanding a refund and stating that I would proceed with my action via MasterCard if this was not immediately forthcoming. I have now received a full refund from the vendor.
Whether or not you believe the vendor's version of events is up to you, but I've recorded it here out of fairness, along with the fact that he refunded me. However, I certainly won't be dealing with him again.