04 Sep 2014 5:45 AM:
As they have written to you in the UK I am assuming you are on UK plates in which case reply to them enclosing a copy of your V5,
If you are on Spanish plates send them a copy of your registration document and point out it is not a motorhome, That should do the trick.
If it is on British plates it might open a can of worms depending how long it has been here, and the fine might be cheaper!
Regards
Julian
Community thread:
Speeding fine, car clearly not ours, but the registration number is !!!
--------------------------------------