I was on chat with them for an hour this morning whilst they made me do all the troubleshooting I had already done again with them on chat and eventually the battery died on the garmin so had to give up, will try again later once it has charged for a while.
2 years is an EU thing. https://www.citizensadvice.org.uk/about-us/how-citizens-advice-works/citizens-advice-consumer-work/the-consumer-rights-act-2015/
But also Sale of Goods Act 2015 http://www.legislation.gov.uk/ukpga/2015/15/contents/enacted
Garmin have been good whenever I called up, and I just told them about issues and they've just then offered to replaced.