Their system is very complicated- anything they have in stock in any of their shops or warehouse is on the website. However, if you order it online and it is only in stock in a shop then they take it to the warehouse. This requires them to set up an inter branch transfer, which may take a day, maybe two depending on when they set it up on the computer and when the van does the rounds and when the staff in the shop get chance to dig it out.
When it eventually arrives at the warehouse they log it into stock, then they start doing the actual preparation for shipping. The courier arrives to collect it later that day, or the next day if it’s after something like 2pm. So you order on Monday, it takes a day for someone to find them in the shop, another day for the van to get them, a day to book it in and another day for the courier to collect, which is Thursday or Friday before your item leaves them.
That’s how it works. And, yes, it is utter bobbins. To the point where the staff find it embarrassing.