Bloody rip off, that's per surname so if you're like me when means the missus moved we'd have had to pay twice, as she still had the odd thing left in her maiden name. Sod that, I did the important stuff then told the new owner to give us a call if anything interesting turned up
OP, you need to speak to the DVLA and the Mags to get some more detail. Sounds like an error to me, but either way you need this sorted as this is the kind of thing that ruins credit for years.
If it was dealt with by the Magistrates' Court it won't have an impact on credit - only civil matters such as CCJs impact on credit. But I agree it still needs to be resolved ASAP.