If memory serves me correctly, they have, actually, broken the law, but I am not 100 percent certain of that without investigating further.
I believe the data protection act covers this, if memory serves me you can get the data altered, changed or removed to what it should be or the garage are liable for a breach.
You can read more about the DPA here: http://www.businesslink.gov.uk/bdotg/action/layer?r.l1=1073861197&topicId=1074412952&r.l2=1074448560&r.s=tl
If you click the "Individuals' rights under the Data Protection Act" link in the main body you should find what you are looking for.