A retailer can be busy ducking all their legal obligations and telling you that you're long past the window of refund, but mention the provisions of the Sale of Goods Act and you usually get a very different response, or a manager is called over (to authorise the inevitable refund). The Sale of Goods Act is still law (Well, parts of it), and the newer EU Consumer Rights Act is in force as well. Good job too, the Sale of Goods Act is stronger in several areas, whilst the EU gave us 2 year warranty.
There is case law where things have been judged to be within reasonable expected life, and a repair, refund or compensation ordered long after the mandatory warranty ran out.
https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CEL...
For example I'm in Denmark and we have a consumer ombudsmand were you can make complaints about violations of your rights as a consumer https://www.consumerombudsman.dk/about-us/ (it talks about marketing but I the Nest was marketed to have functionality it no longer has), in fact there may already be sort of an Ombudsmand ruling that pertains here https://www.consumerombudsman.dk/media/46530/2016-memorandum... which says you can return something after your normal right of return but you are liable for diminished value - so you would not get the full refund in this case but something.
Of course I think that an actual complaint on this subject would result in a memorandum that you can get your full refund.
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