I used XE Trade for the first time last week because I just found out that my US bank will start charging me $3 a month if I don't have a minimum balance of $250, so I had to transfer enough money over there to meet the minimum.
It was fairly straightforward... I used my passport for the first ID, but it wouldn't let me use my driver's licence for the second one... I had to chose a different form of ID. It gives you different options for each ID: the first one I could chose my passport or driver's licence and for the second one, I can't remember all the options, but one of them was a utility bill I think (the 'sign up' section of the site is down for maintenance at the moment, so I can't check it).
You just have to enter all the details of the ID on the online form and then submit your application. Then, if they need further evidence of your ID, they will call or email you to ask for it. I just had to email them to confirm the reason for transferring my money and that was it, the account was approved within a few hours

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I filled out the account application last Sunday, they emailed me on Monday morning and the account was approved on Monday afternoon. Then I arranged for a wire transfer on Monday evening and the money was in my US account by the end of Tuesday

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I did have to pay a fee of £12.50 for the wire transfer (whereas EFT and Draft transfers are free), but that's because I needed to get the money into my US account within 48 hours (by Wednesday) and I didn't have time to wait for an EFT/Draft transfer to go through.