Vav,
I am straight with the UK IR. I was investigated 2 years ago. It was fine in the end but worrying to and the accountants fee was a wee bit expensive.
My way is for non UK citizens and its legal.
I have heard expats say they tell the IR nought. Most get away with it but I know a few who have not, they had very worring times while it was sorted. Not prison but it was expensive for them, accountants fees, loads of paper work to produce for the IR,then finally tax with interest etc.
The IR, once they get into it don't give up until they are satisified all avenues have bee checked out as you well know.
Safe and straight is my moto.
LoL,
GD