Click and collect at Asda or other shops

Hi guys I just wanted to ask I seen some pots on Asda website. When I went to 2 different stores they either didn't have it in stock or it was a different price not sure exactly if it was the same product as online, My question is if I order it to click and collect they charge a fee and I had other items to get it over £25, would I still be charged the collection fee if this item wasn't available but the rest of items where or do they refund the click n collect fee if some items are not in stock as essentially you are paying for a service but it would be some items missing if they can't have everything available to collect or will it definitely have everything I order thanks.