Will an iPhone work if I did this?

In December I will be going to New York. Last time I was there I had a fair amount of money left to spend so I spent it in the Times Square Virgin Megastore. Now that it's gone I'm considering purchasing an iPhone and a universal sim card changer. Would it still work when I return to the uk if I insert my current sim card? (It's an orange Pay as You Go sim card, I'm a british citizen)