Why Britain would resist restoring union with Hanover

What if Queen Victoria died in 1838 and the United Kingdom returned to personal union with Hanover under Ernest Augustus?

The British government would probably find a way to prevent the union or require Ernest Augustus to renounce Hanover before accepting the British crown.

A restored personal union with Hanover could expose Britain to unwanted and expensive European wars. Ernest Augustus had also weakened his political position through repeated demands for money and opposition to Catholic emancipation. In the account given here, he drove Wellington to resign but could not assemble an anti-Catholic government, leaving the king to recall Wellington. The later Regency Act of 1840 is invoked as another example of resistance to his exercising power in Britain; it postdates the hypothetical crisis of 1838. If Victoria died before producing an heir, the suggested response is an arrangement that excluded him or required him to surrender Hanover. His control of Hanoverian forces is raised as a source of potential trouble in a domestic confrontation, even though an attempt to impose himself is judged unlikely to succeed.