Sometimes when cycling on a two lane road in London, I have to stop for lights at a junction. I do not wish to turn right at that junction, but at another junction which is about 40m further on. I need to be in the right hand lane in order to do this - there would be too much traffic to get past if I was on the left. I can't indicate at the lights that I am turning right, as this would suggest I am turning right at that junction. So I indicate once I have passed this first junction. However cars behind me get very frustrated at me using the right hand lane. It's a 20mph zone so they shouldn't. But they do. How can I better indicate my intention to them? Is there anything about this in the Highway Code?