I feel that there is no right or wrong here. I was asking only instead that advice was provided in how to feel ok with this hurt. From listening to everyone's responses I see there are differing views on a couple of things.
While some, like me, value staying with family, many seem to dislike this. This is the basic issue that is causing the difference of views around what to do. Neither is right nor wrong, but it is a fundamental difference that if you are planning a long term relationship with a person is going to cause some kind of strife. This is a concern to me.
The other point of difference is whether or not to do things occasionally that your partner wants to do, even if it's not what you would spend time on. I believe that this is important in a relationship. Obviously not all the time, but on occasions for our partners I feel it is part of a relationship. Others of course may disagree. In terms of the theatre trip, no I wouldn't choose to spend money to fly overseas to see a show I've seen before in a city I already lived in for years, but I am happy to go as I know my partner really wants to go. I didn't do it thinking of this trip to my family, but am surprised to see that DP wouldn't also travel to something that matters to me. So this is the second point where people have differing views.
I think someone said perhaps I wanted to show off my partner...I'm really not sure what is meant by this as my family has already met my partner. I of course would want them to get to know each other though, as family.
Thank you all for your input, I do appreciate it. I guess that we have some clear differences on what we each expect or do not expect in a serious relationship. This is something for me to think on.
Oh and I know that 18 months sounds little....it certainly did to me when I was in a 23 year relationship, but for some reason this does feel like the real thing and it is serious, despite the short length of time!