Apple TV+ launched on 1st November 2019, and if you purchased an iPhone, iPad, Apple TV, iPod Touch or Mac (iMac, MacBook Air / Pro, iMac etc) after 10th September 2019 then you will be eligible for an Apple TV+ 1 Year Free Trial!
NOTE : You only have a limited time to take up this offer. I believe that limited time is 3 months so do not hang about too long.
However some users are reporting that when they go into their Apple TV app on their device it seems to only be offering 7 days of a trial – then the billing starts at £4.99 / month.
There is a very easy work around for this issue (I was one such user who experienced this).