It certainly used to be the case that you couldn't get fined if they hadn't physically put a ticket on your car, but that changed in 2008 and since then they don't have to put a ticket on PROVIDED they have evidence to prove an offence took place. From the government's own website:

http://www.patrol-uk.info/site/scripts/faqs.php?categoryID=1&faqID=4#a4

You could be lucky in Blackpool that the traffic wardens don't have cameras and so they have to still physically stick the ticket on.
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