I also live in europe, but in another country. I bought my SN from canada,too ,maybe we bought it from the same seller. I wrote them an e-mail in which I asked them, if they think it could lead to problems with customs or if other customers had problems related to that issue. If you want, I could pm you when they answer it.
But if SN is legal, customs probably won't bother you.
Of course England isn't part of the EU anymore, but I don't know if there is a huge difference if you buy something from canada.