The like-for-like replacement is covered for legally under consumer protection. The 'upgrade' to the latest one is not & will be viewed as such under due process.
Whether you view the original as 'fit for purpose' will be a court room argument requiring much evidence.
Any legal expert will tell you it's far better to enter court on the basis of how much it will cost you, not a principle.
It's up to you Karl, but I'd be attempting negotiation first..
