Which UK plant are you coming from?
I'm originally from Scotland but now live in the U.S. and work as an HP - I also did this in Scotland, at Hunterston Power Station. I married an American, though, so that's how I got here.
Before coming over, I had contacted Bartlett and was basically told, "Get here, then contact us and we'll be able to put you to work." Not really much help.
There is a definite shortage of HPs over here, which may help you, but believe me, it is incredibly difficult to get Work Visas etc. for the U.S. I had even tried to get Bartlett to set up some sort of exchange programme with RadWise (and there's now also Nuvia) but they didn't seem too interested.
I saw you mentioned DoE. I was told as a non-US Citizen, even as a Permanent Resident, that I couldn't work most DoE sites. That was around 5 years ago, but I haven't tried since. Just make sure you check it out before getting your hopes up.
Would Canada interest you? As far as I know, there's a lot of Brits working at Bruce Power on Lake Huron. Just a thought.
If you have any other questions about us ex-Pats living/working here, just ask. I'll try my best to answer you.
Good luck and "Best of British"!
Jon.