One of the few local suppliers which seems to have some timber I want has been Wickes.
I assembled my order - three different products - and tried to book delivery and pay.
I got a message saying no slots - they release slots every day, so try again tomorrow.
OK - do that. Twice. Getting nowhere absolutely not a single slot available.
Eventually realise that it is only saying no slots for one product. So I remove that and add the equivalent (different lengths of the same timber). Now one of the other products is out of stock. Substitute that as well, and eventually get a slot and pay.
But why do they tell me no delivery slots for a specific product? When I can get effectively the same product by changing lengths? I can see that if the product is out of stock, they expressly tell me that! It isn't even as if the products require a longer lorry rather than a van, or whatever. Some of my successful substitutes are actually longer.