Just a warning for those hoping to pre-order today to try and avoid the official Microsoft website if possible as it was an absolute mess for me earlier this morning. Pre-orders opened here at 6am this morning (11pm yesterday UK time) and I had two websites ready to go; one was the official Microsoft site and another was a well know local tech chain store.
The Microsoft site had the pre-order become available slightly before the chain store so I ploughed ahead with that one only to encounter error after error when trying to confirm everything on the final page; shipping address, billing address, card details etc. This was particularly annoying as I use Microsoft regularly so all of my details were already there. Once I finally got to the confirm purchase point the whole thing crashed, the XBox Series X dissapeared from my cart and it was now sold out.
I then went back to the other retailer, Hachi Tech on behalf of the Challenger Stores, who had now got their act together and had them available to pre-order and managed to purchase with no problems within about a minute.