My character has swiched servers/world?

I cant remember which world I picked, but I know it was an (EU) one, possibly "Phoenix".
This morning I had some issues logging in and it kept saying "couldn't update JP" or something, eventually after about half an hour of logging out and in, it actually loaded up my character for once and instead it now read "couldn't update NA/EU". I figured it was nothing and pressed start, but eventually noticed all the names around me are Japanese and nobody speaks English in this world (Kujata?). How can I switch back to an EU world? My connection and sociability are pretty much dead at this point :p

Well you obviously created a character on a Jp server. Log out, and at character selection screen click on world and scroll down there will be a number (not zero and likely 1) on the right of the listed server worlds, that's where your original character is.

Next time don't just blindly click buttons, you should have noticed that when you did this the EU/NA servers were down and it randomly chose another server for you, on the JP servers.

I only have this one character, I created him on the Phoenix EU server. I didn't "randomly click buttons" , when I said I 'think' I picked Phoenix, I was referring to the fact that I'd forgotten my worlds name at the time of posting this, not that I selected at random. If I may elaborate clearer, This morning I couldn't see my character at all, he wouldn't appear, eventually after repeated log in attempts he was actually on screen and I could select him (at this point and at all other times, Phoenix was in the top left of the screen as my world, even when My character was not present). I tried to start the game and it told me I have to wait because the server (Phoenix) was full, eventually it let me play, or at least I thought it did, now I'm in Kujata somehow and I at no point chose this.

Just to make sure I'm not mistaken, I've been character searching on the website, names of people I remember talking to/passing by yesterday, they are all on the Phoenix EU server, if that helps.

"(Phoenix) was full, eventually it let me play, or at least I thought it did, now I'm in Kujata somehow and I at no point chose this."

So you just proved what I said. Let ME be clearer. Phoenix was full, you got an error message likely, 1017 perhaps. You try again it lets you in. It only let you in because when the EU/NA worlds are unable to update it provides the option of defaulting to JP worlds. It gave you a random one. You clicked it, and it made a character there. That is the only way you are now on a different server. It chose the server for you, so technically you didn't choose it, but you chose it by clicking log in without checking.

Like I suggested. Go to the world list, under NA/EU and find Phoenix, there should be a (1) next to it indicating you have a character. Make sure it says Phoenix when you are ready to log in. Likely though, it's full, they are all full for everyone right now...

Additionally: If you get a red message that says EU/NA unable to update servers or whatever it says, don't just click log in, you'll be in a JP server again. Make sure you have chosen Phoenix as your server.

My character isn't in the Phoenix EU, the list is all zeros except for the one in Kujata (My original and only level 10) , I've checked that a few times now. It said Phoenix was full yes, It would start loading and I'd have the pretty backdrop and the mail Moogle in the corner, then it gave me the dreaded 1017 etc.
It backed me out and said there was 184 people in the queue, and the only option was to click cancel or wait. I waited and it went to 178 people and soon after the screen went black and I was being put into play, eventually I noticed every bit of dialogue people spouted was Japanese and none of the surrounding names were familiar.

Well then I don't know what to tell you. Remake the character on Phoenix? If you want to wait until monday or tuesday you can call customer support.

Unless they put a system in place where if the others are full and you create a character on a new server (in your case by accident) it moves the character to the other server? I don't know, haven't heard about anything like that.

When you say remake, do you mean a new level one, or can I clone? As you said it had duplicated my level 10 to Kujata, I'd assume I myself can also put him back or copy him somehow. Well thanks for the time and advice anyway, even if it did come across a little condescending. I'll have to call support on monday. I suppose I should have known not to buy an MMO on launch day, given FFXIV's notable history...