It went through the process of eclosure (hatching to you and me), last night sometime - possibly very early this morning, and emerged a plain orange colour with very little marking indeed.
Over a period of 7 hours, it stayed by its pupal case, hardened up and formed its spots as can be seen by the series of photos below.
This is how all Ladybird species form their spots. They emerge from their pupal cases without markings, and develop them over their first day as an adult...
NB. After a little research I have discovered that most of our native species of Ladybirds should pretty well all be in adult form by now, having one generation per year. This year seems pretty strange anyway, as there are some of our native Ladybirds that are still in larval or pupal form at the moment. Whether they survive the winter is a tad doubtful.
Harlequin Ladybirds however, (not native remember) have up to 3 generations per year (another reason why they may well become problematic for our British fauna), and the Harlequin Ladybird can still be found in larval and pupal forms (like the recent photos on "Blue-Grey") all over Britain, as far north as Edinburgh.