Yeah… look, if you’re going to take on the aggressive tone, it helps if you also know what you’re talking about. So let’s go through this.
First, you’re right to say that the UK issues its own currency — or, rather, in the main its banking system issues money when loans are made. But that *does not* alter the constraints the economy faces: it just changes where they will appear. Should we, collectively, wish to finance greater purchases from abroad than sales, we need to finance this. Net income can be one part of this, and for much of the 2000s net income was positive, shrinking the overall deficit. Lately, it has swung negative, pulling the current account further into deficit.
That deficit is a financing constraint. Whilst we, collectively, are at perfect liberty to issue as much money as we see fit domestically, there is no requirement for the rest of the world to believe that this money is worth much. (We’ve already seen how QE — issuance of greater volumes of money by states — has caused devaluations.) In practice, the deficit can be financed by trading real claims on activity here — borrowing, or selling assets. That, of course, adds to the future outflows, worsening the future current account deficit.
Because the current account concerns relationships between, rather than within, national economies, it can’t be treated the same way as other deficits, that can be met by domestic financing of one sort or another. If left unmet, it will act as a constraint on domestic activity, potentially rather suddenly. (See, for instance, this comparative account of “sudden stops” in Europe: http://www.voxeu.org/article/mother-all-sudden-stops)
Finally, the interest rate on government bonds very much *is* determined by the markets. I’m not sure why you’re trying to claim otherwise. QE has shifted the price of borrowing somewhat but it does not determine the price alone. (This early study from BIS suggested that QE reduced long-term government bond yields by 100 basis points: http://www.bis.org/publ/bppdf/bispap65p_rh.pdf)