If you would rather just ignore this then do so, it's your choice. CP Plus are not known to try small claims but you would of course just need to be aware to keep all letters for years, and certainly not to ignore a small claim if the papers did arrive one day (as has happened with Civil Enforcement and Parking Eye recently, regarding old ignored tickets).
If it were me I would appeal (once you get the first letter to registered keeper in the post ONLY, do not respond to a windscreen ticket) and then do the POPLA thing.
Could be as simple as a letter like the one suggested in this thread, to CP Plus; the important thing is NOT to say who was driving or give any information AT ALL:
http://forums.pepipoo.com/index.php?showtopic=79309...then a letter, form or email enclosing a robust appeal like this sort of thing to POPLA (post #4 was my suggested wording for that OP regarding an alleged 'overstay):
http://forums.pepipoo.com/index.php?showto...pid=826768&...but checking back here before sending it to POPLA first, and showing us your draft for help to ensure all points have been covered in your case. We do keep adding more points to POPLA appeals!