I'm a Mexican citizen and don't need any kind of visa to travel to the UK. I can just travel with my passport and stay there for up to 6 months. I was in the UK for 5 months and 2 weeks, from February 1st to July 17th 2017. I was there visiting some friends and traveling around as well.
I would like to visit my best friend in 2018, from February 28th to May 28th, just 3 months. Will I be able to stay in the country again for this period of time? Of course, my friend could give me an invitation letter and prove that I'm staying with him for those 3 months, and that he will cover all my expenses.