This is a problem not restricted to the UK.
Here in New Zealand we are grappling with similar problems. In conjunction with Eastern Europeans we also have ethnic Chinese and other asian cultures that fish soley for the table. They do not understand the licencing regime nor the catch and release ideology, to them that is an anathema as they only understand that fish are food and free food at that.
That is OK with game fishing for trout and salmon where it is normal to take fish for the table up to the limit but when it comes to coarse fish specially stocked in certain waters Oh boy! is there trouble.
Education is the answer, we have ongoing dialog with Russian speakers which is making real progress but with Chinese, Cambodian, Vietminanese, etc we have a real problem.Language being the real barrier to be overcome. If Asian anglers all bought licences the number of anglers would double statistically overnight and real progress might be made to accomodate coarse fishing as a major sport here in NZ.
Old Chinese proverb: "Softly softly, slowely slowley catchee monkey" and tell them where the best trout waters are!