There has to been so additional discount. Loads of people have done it
i 'think' i know what i did......ordered fairly early after reading post 6 in thread which advised of the £2 off which i claimed and applied....for some reason i didn't apply the 20% but if you at post 6 it has being edited and i wasn't aware of the extra 20% when i ordered. For some strange reason they also knocked off £1.99 and not £2 off my order.
Have you tried stacking therm yourself???? nothing to lose surely as your £2 of is a unique code and i would imagine only expires on use.