I love how manufacturers like to hide behind ‘you didn’t register for the five year warranty’ Stuff. Manufactures make all sorts of demands on consumers on what they have to do to have a warranty. All complete waffle. So, what would I do, this would be my solution and I’m not recommending it or providing advice. Right, so the disclaimer is now in place
As I understand it, (I used to run company making consumer products, but that was over seven years ago before I retired ) manufacturers are responsible for their products for the reasonable expected life of their products to ensure they are material, design and manufacturing defect free. For the first year, it’s up the manufacturers to prove the unit wasn’t faulty, after that it’s down to the user. I would have taken photos of the installation and have records of who installed it. Second I would write to the manufacturer or where ever you bought it with a 14 day letter, (lots of templates online) explaining the reasonable steps you have made to ask them to resolve the problem, that you’ve been forced to replace it and ask for the total amount you’ve had to spend including installation to be refunded. They wil either pay up, offer a solution ie a payment somewhat less than your asking or ignore you. If you don't accept an offer, or they ignore you I would take the case to the County Courts. Now, it’s very easy to do, takes about 10mm online, BUT it’s not free, we are taking a hundred or so pounds depending on how much your claiming. But if you win you get it all back. Your case is simple, it’s failed after being professionally installed within two years and the manufacturer offer a warranty for up to five years. Now, this is almost certain to grab their attention. The courts love to bash company’s so the chance of them winning versus the damage and cost of defending the case is what they balance up. If your seeking less than say £1K it’s always in a company’s interest to settle out of court. However, if they don’t, you literally get a day out at the courts which is all very low key, intersting and you don’t need a lawyer.