You can opt out of Click & Collect altogether, or just exclude certain listings.
To opt out altogether, go to Site preferences in My eBay. Edit the Click & Collect option and select opt-out. You can opt back in at any time.
To exclude a particular item, look for the check box in the Postage and payments section when listing or revising the item. You can also use your business policies or listing tools to set postage preferences for individual listings.