Apparently chargers can't be bigger than the dimensions given for phones on Turkey to UK flights as per the new security regulations.
I thought I would share this with you - a flat, 4000mAh charger block, about the thickness of an iPhone and smaller in length. 4000mAH isn't massive but enough to see you through the flight home.
Found in B&M and even better, not £5.99 as shown, three quid...!