I don't think it's a UK thing only. I'm in Ireland and, no matter on which day I place the order, they will not "process" it until Thursday and ship it on Friday which means I am getting the product the following week. Sometimes, shipment will not occur until the following Monday which then means I will likely not get my order until Friday, which leads me to think that there are delays not just on how fast they dispatch but also in the shipping process too.
Maybe with the UK the issue is Brexit and maybe with Ireland the issue is that it's a smaller market? No idea but I really like Thomann for their prices and assortment but despise their processing and delivery times.