If I change to Saturday delivery tomorrow (Friday), assuming that my PC build is ready by then, is it possible to receive the order the very next day? And, if so, by what time on Friday do I need to change to Saturday delivery?
I would ring them to clarify. If you call early on tomorrow they’ll likely be able to advise what stage your machine is at and whether not not it will be despatched. We can only speculate in here.