I remember the so called "Cod War" with Iceland back in 1970's

I can't really recall all the detail, but Graham is right in that no-one would help or support us.
The UK government eventually conceded and our fishing industry was never the same again.

I remember cases of boats ramming each other and fishing nets being cut. Then naval ships on both sides got involved.

Same principle then as China has done now, unilaterally declare extended territorial waters then impose a fishing ban.