31 year lows for the pair
The GBPUSD has traded at levels not seen for 31 years. That makes defining a bottom difficult.  
Looking at the daily chart, however, because we can draw trend lines (and channels), we can project targets by connecting lows.  In the chart, the lower channel trend line cuts across at the the 1.2696 level (let’s call it 1.2700).  That is the next target from a longer term perspective.  If the trend continues lower, that line will come in play (PS the low today got to 1.2718 so far).