TFL have been breaking the data protection law for some time now by paying European agencies to chase people for London Congestion Charge fines,i have even heard of people getting hounded in Europe for Dartford crossing charges.They are raking in so much cash they can pay all these companies,no problem.Nobody seems willing or able to take them to court over it.
If you live abroad and have a foreign registered car there is no requirement to pay a claim from a debt collection company for a penalty issued in the UK
Of course, if you did commit the offence you could pay TfL or Dart. 