I know that things like this can be very stressful, but let's look at the positive aspects of all of this. Yes, the costs for moving overseas can add up, but you have a year (Sep 05) to save some money...as does your Fiance. That also means that you have a year to decide what you want for your wedding...how big? what country? what sort of budget? And remember, it's not the wedding that is important, it is the marriage, so even if you have to make one or two small sacrifices on the "dream wedding" as long as it's a dream marriage, it won't make a difference (however, that means small sacrifices...if you really want a church wedding with the big fluffy white gown, don't conceed to a registras office in a summer dress...)
Here are a couple of things to look at (ideas I've thought of for my own situation). If you are going to be living in the UK starting Sep 05, and you KNOW that now, then concider sending / taking stuff over when you visit your fiance or when he comes to visit you, send him home with stuff. That will save on shipping costs, and can work both ways if he is to move Stateside after the wedding.
Myself, I am getting married in May of 2005, so I understand many of your fears and paranoia. My parents are of humble financial background, so the whole wedding, visas and relocation thing is on us (though we don't yet know if we will live in Scotland or Seattle). I am lucky in that Paul makes a decent wage and I just got a great job so we are both able to save money for the impending events.
I'm sure that things will start to feel more secure as you get a little closer to the big day. We are always here if you need us!!