Dec. 5th there will be 1.3 Million new ordinary shares (London) as part of the employee stock incentive programs. Less than 1 percent dilution, but still seems to have spooked investors. Look at the chart for GWPH.L - this was announced Nov. 29 and the stock immediately headed lower. Probably a good opportunity.
I think more than anything right now this stock is in line with overall market sell off. DOW and NASDAQ both had selling going on today, but stabilized at the end, much like what GWPH did. GWP.L follows in suit some days of GWPH and other days it wanders in its own direction. In the long run you will want to stick around, no doubt.