They have now apparently changed their mind on this, at least according to this post on pepipoo.
Due to the nature of your request for information we are unable to provide this via email under the Data Protection Act. However, data-subjects have the right to request information held about them by the DVLA. Requests for such information from the vehicle record must be made in writing providing full name and address and details of the vehicle registration mark(s). The fee for this service until today was £5, but this is now a service which is provided “Free of charge”. Requests should be sent with any necessary documents to: Vehicles Fee Paying Enquiry Section, DVLA, Swansea, SA99 1AJ."The Prankster welcomes this change of position - it is only fair that keepers know if a parking company has correctly accessed data. Going further, it would be even better in future if a keeper could register to be automatically informed if an operator has accessed their data. The Prankster suggests that email would be a cost effective method to do this, with post as a back up for keepers who do not wish to rely on email. This can be easily funded by the current charge to the operators of £2.50.
The Parking Prankster