I had an x-ray a couple of weeks ago at the veterinary practice and the total was almost £150, plus since I don't have transport, £40 to get her there. The x-ray is covered by insurance. I don't know how much mobile x-rays are.
If the X ray is covered by the insurrance, chances are your transport is too - so long as you used a registered transporter or are claiming for your own diesal
Mine charges £10 per shot, £10 per xray interpretation. This was at the clinic though, dont know if theyd charge xtra to take machine out on top of normal callout!