You were right the first time if you were think of BA CW. If you're sitting in a K seat then you're facing to the rear of the plane and the from your perspective the seat is the left-hand-side.

If you approach from the East the views on the K side are spectacular. If you've not seen London before this way, I strongly recommend it. You need to take a local with you (what's the Air NZ hand luggage allowance? ) to point out what everything you're seeing actually is. I can wave at you from my balcony (just north of Trafalgar Square). If you're very lucky, my lovely neighbour will wave at you from her much grander balcony at the end of that street leading SW from Trafalgar Square.