Tam,
This is exactly why you will need to be in the States to interview in person. The pay will depend on your qualifications, any welding certifications, the amount of hours you work per week, etc. If you make $90,000 per year, I would suggest you send for your girlfriend and have her move to the UK. Why would you even consider leaving a $90,000 a year job? I seriously doubt that you will make that in our refineries working as a "plater".
CM