Why do you thing that things like stepper motors, drivers and leadscrews are only available in the USA?
The plans may lave links to parts in the USA, but this is because these are the parts that they recommend and this maybe because the plans were put together in the USA.
Leadscrews are cheap in the UK as well as stepper motors and drivers.
Also i would say plans are typically not worth the paper they are printed on, and looking at the sidewinder CNC, i would bin the plans and start from scratch, just look through the forum and follow the build logs.