Three things need to be said before we look at what Mr Helgesen said. Firstly, the country he represents is not a member of the EU because its people have consistently voted against that membership; secondly, the country has remained an active player on the international scene; and thirdly, despite what the article says, Brexit has not been "high on the British election campaign agenda" precisely because David Cameron promised "an in/out referendum on the UK's EU membership if he is re-elected". What was relatively high on the agenda was the referendum and whether one should be held. The question of Brexit itself was neatly shelved for the time being.
Nevertheless, it seems that Mr Helgesen is sufficiently worried to issue a warning.
But Helgesen says there are some important aspects of EU membership that have been left out of the British debate so far.I am not sure what of the debate Mr Helgesen has been reading but the questions of defence, security and foreign policy have come up a few times and discussed from various angles.
For example, a British exist - or 'Brexit' - could leave the UK out of the comprehensive trade agreement being negotiated with the United States.
'Brexit' would also leave the UK out of important EU foreign ministers meetings addressing the standoff with Russia over Ukraine.
“Leaving that position of influence… I have a hard time seeing that. I don’t think it would serve Europe, but ultimately that is the British people who should determine that,” he said.
As for the position of influence (I am aware that I have not completed my discussion of that subject), one has to say that within the EU's common foreign policy Britain has about zero, unlike the influence and, indeed, the choice of action it has within NATO.
Still it is good of Mr Helgesen to admit that it is the British people who should determine that. Just as the Norwegian people have determined twice that this was not for them.