I had both of Harrys forlegs done; over all for the x-rays + examination + call out was about £200.
And I got to see his leg's on his laptop screen, also he emailed me pics of the x-rays. - they were amazing!
Our vets have portable x-ray machines so they can be done in the field, making life easier. You would have to have mains electricity though as i've known them blow up off a generator!
Mine has just had one foreleg done, they do both so they have a comparison. Mine came to £160 for x rays + £10 for sedation. That was taking her into the hospital