In the absence of legal precedent in the UK, we can look to other countries with similar systems. In 2009, the Federal Court of Canada heard Conacher v. Canada, which was brought by a citizen-advocacy group after Prime Minister Harper asked the Governor General to dissolve Parliament in advance of the date specified by the Canada Elections Act. The court found that this question was basically non-justiciable; while Crown prerogatives can be reviewed, they must violate an individual's rights to be justiciable:
The case of Black v. Chrétien, above, shows that the Federal Court has jurisdiction over direct exercises of Crown prerogative because they emanate from a federal source. Although some prerogatives are reviewable, the Court must still determine whether a particular prerogative is justiciable. The hallmark of justiciability is whether the exercise of prerogative affects the rights or legitimate expectations of an individual. In the present case, no legal rights or legitimate expectations were affected, other than a claim having been made under the Charter, thus, the Prime Minister’s advice is not reviewable.
(Styling was present in the original, though the bold text was underlined there.)
Prorogation and dissolution of parliament are both Crown prerogatives under the Canadian (and UK) systems, and it is difficult to see how a prorogation would violate the legal rights of an individual any more than an early dissolution would.
The important difference between the UK and Canada, however, is that Canada has an explicit written Constitution and a Charter of Rights and Freedoms, while the UK constitution is largely (entirely?) unwritten. The legal reasoning applied by the Federal Court rested heavily on the Canadian Constitution Acts.
It is important to examine the constitutional context because Canada has a system of constitutional supremacy that lays out the boundaries of Parliament’s power. In this case, the constitutional context is that the Governor General has discretion to dissolve Parliament pursuant to Crown prerogative and Section 50 of the Constitution Act, 1867. Any tampering with this discretion may not be done via an ordinary statute, but requires a constitutional amendment under Section 41 of the Constitution Act, 1982, which requires unanimous consent of all provincial governments as well as the federal government before a change can be made to the “office of the Governor General”.