Should point out they only want max 12 weeks reducing to max 6 for Pfizer one due to manufacture data (they didn't do any trials with longer gap than 3 weeks as you said iirc).
For the oxford one, they ain't asking it to be shortened, because even though the manufacture said 3 weeks, their trial data actually shows a longer gap of 8+ weeks made it
more effective! (~90%+ as opposed to ~60%+)
Pfizer are also having manufacturing problems due to currently restructuring their facilities to be able to produce 2 billion doses this year compared to the original 1.2b, but are having down time right now.
Italy are on about suing them as they are not going to get the doses promised! Think UK more weighted to oxford one which should have less capacity issues in theory ?