GBPUSD - 15m timeframe, how I enter...

The timeframe I enter my trades on with an explanation as to how. The candle highlighted in yellow is the last bearish supply and demand zone prior to the big move down. Once the low of the move can be identified (highlighted in red here) then the fib can be drawn. From this price action is monitored at the 0.5 and 0.618 fib levels. As we can see here the 0.618 was respected very nicely and so shorts where entered. Stop and take profit can be seen clearly on this analysis. Nearly a 2R trade and this works very well on all timeframes. Thoughts?