This may be a calculated risk. Hopefully they did more due diligence, but a quick search shows a Dec 2011 case [1] where an estate business was prosecuted for collecting info, but was fined a small amount (< £1,000). The extenuating circumstances were that they had already complied with the law by the time the case was heard by the court.
[1]: http://www.ico.gov.uk/news/latest_news/2011/estate-agent-pro...
It seems they may have broken the data protection act in more than one way.
* First, they collected personal data about UK citizens without their permission (as a 3rd party cannot give that permission),
* Secondly, personal information was kept for longer than is necessary (it should have been deleted after it was used)
* Thirdly, they allowed personal data to leave the EU.
Note that personal data includes name and address, telephone number or Email address.
http://en.wikipedia.org/wiki/Data_Protection_Act_1998