If I am not mistaken, the £1 would typically be distributed between all of SVB UK's current shareholders. If SVB UK is 100% owned by the SVB parent company, and SVB parent is bankrupt, the £1 will get added to the funds that will make the SVB parent's creditors "whole", who outrank shareholders in bankruptcy.
And yes, the £1 has to get actually transferred, it is important for legal certainty e.g. with regard to https://en.wikipedia.org/wiki/Consideration_under_American_l....