Hi Joe,
From what I've seen, CV's and Resumes are really the same thing. If you're applying with agencies, they're going to create a new CV from the information you gave them and that's what they'll send the employers. So you don't need to worry about that.
Unless your CV is so ridiculously written up, it's not going to make an enormous difference to the employer. I notice you're still in the US. If you can't work immediatly here, that'll make a difference. Employers will rarely take a second look at an applicant who can't work here legally. You need to look into a visa before you look into work.
I'm a little concerned for you because you want to come here on a work visa and the IT business is really bad at the moment (I asked hubby, he's in IT). I can't say with authority, but I think, even with your credentials, you'll find it difficult, if not impossible, to find work in the UK.
However, don't give up if it's what you really want. Have you looked into American companies willing to employ and send you to the UK?