As far as reposting the item again to the buyer, once its returned, i'm afraid that would be down to you, because the buyer has already paid once and expects the item, the fact the garage doesn't accept items anymore isn't their fault or problem. As far as the garage is concerned, i would give Ebay a ring and point out whats happened and why they are still listed as an option and what, if anything, they may or may not do about your wasted postage costs.
This is why i have never used the click and collect service or GSP, too many cooks in the kitchen 😉