What are the advantages of a codified constitution?

Codified Const would be intentionally difficult to amend:
It could be said that Parliament should not be able to make fundamental changes to the constitution w/ only a simple act of parliament – since 1911 Parl. Acts, not even HofL can prevent a govt w/ support of the majority of HofC from amending Const.
Intentionally difficult to amend = ensuring that amdts would receive intensive scrutiny and not undermine the n constitution core principles.
Would stop us relying on political limits to constrain constitutional amdts and help restrain the behaviour of govt. and keep MPs from ignoring the people’s demands.
g., Stop govt from violating human rights in times of emergencies like the Anti-Terrorism, Crime and Security Act in 2001.
An amendment to the US constitution needs a 2/3 majority in both houses of Congress and approval of 3/4 of the states.
It is easier to remove human rights in the UK, such as the plans of the Conservatives to remove the Human Rights Act 1998.
Stop govt from violating human rights in times of emergencies like the Anti-Terrorism, Crime and Security Act in 2001.

Constitutional Judicial review allows the SC to declare legislature as unconstitutional.
Parliament is sovereign and therefore can go against the judiciary when they want.
In the case A and others v Secretary of State for the Home Department (2004), the Law Lords declared that the indefinite detention of suspected terrorists at Belmarsh prison was incompatible with Article 14 of the ECHR because the Act discriminated against non-British citizens.
In response, the government introduced the Prevention of Terrorism Act (2005), which replaced the discriminatory detention of foreign nationals with ‘control orders’, applicable to British and foreign terror suspects.
Following the ruling in HM Treasury v Ahmed and Others (2010), the government introduced the Terrorist Asset Freezing Act (2010), to give them the anti-terrorism powers the judges found they lacked.

We are overly reliant on unwritten conventions that are not legally enforceable and that few understand.
The Government argued that the House of Lords had broken multiple unwritten conventions, including the Salisbury Convention and the Common’s ‘financial privilege’, when the House voted to block its tax credit reforms in 2015.
Many in the Lords, however, took an entirely different view, leading to a brief constitutional crisis in which, ultimately, the Government backed down.
While unwritten conventions have been observed and followed for centuries, they are not legally enforceable.
The Scotland Act (2016) formally recognised the existence of the Sewel Convention – the rule that the UK Parliament will not normally legislate on devolved matters without first seeking the consent of the Scottish Parliament.
However, the Supreme Court ruled in 2017 that it could not enforce this convention, after the Scottish Government argued that a legislative consent motion was required before the UK Government could begin the process of withdrawing the UK from the EU.
It is arguably unacceptable that matters as important as the role of the monarchy, the use of ancient prerogative powers, and the circumstances under which the UK enters into armed conflict, are left to unwritten conventions that could ultimately be broken.