How much funding for the upgrade of the A75 and A77 has been committed by the UK Government.

To date, we are not aware of the UK Government committing any funding for the upgrade of either the A75 or the A77. The UK Government’s Union Connectivity Review (UCR) published its interim findings in March 2021 and identified both the A75 and A77 as critical road transport corridors connecting Northern Ireland with Scotland and England.
At the same time, the UK Secretary of State for Transport announced that a £20m Union Connectivity Development Fund was available for advance design / development on a select number of transport corridors, including the A75. It is not clear if any of that funding has been spent on preliminary work for the A75.
The Final UCR Report was published in November 2021 and recommended that the UK Government commit funding to support the significant upgrade of the A75. The failure to mention the A77 suggests it will no longer be considered a priority for upgrading.