Recently GBPUSD has broken below lower 1st standard deviation from quarterly mean, initiating a new leg downwards.
If the price continues down from here, the closest target is relevant lows at 1.5150
If those are taken out, price will be very likely to fall to the lower 1st standard deviation from 1-year mean at 1.5000
Thus downwards scenario will be only cancelled by GBPUSD spiking back above 1.5500 - the level at which 1-year mean and quarterly mean converged now