Data on government spending with suppliers is available on the Crown Commercial Service website. Departments also publish spend data on GOV.UK and are responsible for their own hosting decisions.
As part of the One Government Cloud Strategy, the government has already agreed a number of Memorandums of Understanding with suppliers including UKCloud, Microsoft, IBM, Google and AWS.
The Government is assessing the need for any actions arising from the Schrems II decision. Further announcements will be made in the usual way.