This, and again, not to pour salt in the wound. But why didn't you just go?
Agree. You have to assert yourself over your family. You are an adult now, and you can't keep letting them control you like this. They need to learn when to let go. My mother was terribly upset the first time I was going to travel alone, at age 19, to the point where she wound me up at the airport, telling me she knew the plane would crash. I nearly had a panic attack, but I told her off and got on the plane anyway, even though she had me so worked up I was terrified. It was the best thing I ever did, in my opinion, and I had a great time.
Unfortunately, you don't get a do-over on this one, but if I were you, I would tell my uncle to shove that his offer to buy your boyfriend a ticket up the whazoo, that I don't need his help, that I am sick of my family interfering in my life, and I would probably try to find a way to get another ticket on my own, no matter how long it took, and tell them to sod off. I wouldn't let them have any control over how or when I saw my boyfriend, if it were me. But, you have to decide for yourself. You really need to stand up for yourself, though, and do what's best for you, not let them convince you that THEY know what's best. Good luck to you.