Some rules to live by:
Ignorance of the law is no defence.
If you are a gun/hunting guy you know these rules to:
Always know the rules of the jurisduiction you are entering.
Never bring something across a border that: a) you don't declare; B) aren't sure about its legality.
An hour on google would have saved 3 weeks in jail.

An ounce of prevention is worth a pound= 0f cure.
Are supressors legal in the UK. I don't know. If I am tempted to bring one in I'll check first!
My guess is they are not!
BTW Why does a hunter need a supressor?