DEFINITELY visit the UK before you pack up your life and move. And try to visit in the dead of winter when we are having short, damp, grey days. Unfortunately no matter what you do, it'll like be a "holiday" and not a true test of what it's like living here. But you likely won't know if you can do it until you try. But the UK is not for everyone. Just like the USA isn't for everyone.
I was in England in February/March planned to stay for 2 weeks. During those two weeks, the Beast from the East hit the UK and we couldn't get to the airport!! I had to move my flight (they didn't charge me due to a natural disaster, score!) but they couldn't reschedule for an entire week! Which seems great, but I also didn't get paid for 3 weeks
That being said, when my husband had to go back to work for my unexpected week there, I spent a lot of time in town alone, walking around, exploring, visiting coffee shops (I am a coffee enthusiast) etc etc. Gave me a really good idea of what it's going to be like when I move there and I'm unemployed for a little while.
I know it's not the -same- as living there, but all it did was confirm how much I absolutely love the UK.