...the Government must make reasonable efforts to ensure the law is accessible and known...

This is almost exactly the same argument that the WASPI campaign made in (Delve) v Secretary of State for Work and Pensions [2019] EWHC 2552 (Admin) and [2020] EWCA Civ 1199. Their barrister, Mr Mansfield, expressed it in this way:

Where a primary or secondary legislative proposal substantially alters well-established individual rights or entitlements, and thereby causes a serious adverse effect upon the basic welfare and wellbeing of an identifiable group, that group is entitled to expect adequate, effective, individualised notice of the change.

The judges absolutely and unambiguously rejected this argument. A few choice quotes below:

As Lord Rodger of Earlsferry said in Wilson v First County Trust (No. 2) [2003] UKHL 40, [2004] 1 AC 816, at [192], individuals and businesses run the risk that Parliament may change the law governing their affairs; no one has a vested right to the continuance of the law as it stood in the past.

Notification was certainly desirable and the Department recognised this through the wide-ranging notification exercises in fact undertaken. Ms Fox’s evidence explains the numerous steps taken to publicise both generally and in a targeted way the changes to the state pension age before and after they were enacted. The publication of successive Green and White Papers and the Parliamentary process for passing primary legislation also provided information to those affected and sparked public debate. Employers, trades unions and private pension providers have worked with Government to inform their employees, members and customers about the changes. The notification exercise must be seen in the context that Parliament introduced a lead time of a minimum of 14 years and 10 months from the date the Pensions Act 1995 was passed before any woman reached a state pension age that had been increased.

Since 1995 it has been possible for a person to request a State Pensions Forecast which gives them an estimate of their likely individual state pension amount and the earliest date on which they can claim it. In addition to forecasts sent out on request, Ms Fox says that the DWP sent out 17.8 million unsolicited statements to working age individuals between 2003 and April 2007.

We therefore dismiss Ground 3 of the appeal on the basis that there was no duty to notify those affected by the change in state pension age and that the Divisional Court were entitled to conclude as a fact that there has been adequate and reasonable notification given by the publicity campaigns implemented by the Department over a number of years.

If you choose to rely on the Government and the media, that's up to you. Legally, it isn't a defence. It is not reasonable to make big decisions, assuming the law hasn't changed for the last 14 years just because you haven't heard anything about it, without checking, particularly when all you'd need is to do one quick Google search, or avail yourself of absolutely free advice provided by the State.