Just ordered a bottle. Seems a bit pricey for such a small amount but hey ho.
Seems quite a few houshold products might do the same jobs as some windowcleaning suppliers expensive products.
eg.
gg3/gg4 - Fairy
MDF - Cillit Bang
Windsol Crysal Clear - Vikial, Killrock, Cillit Bang lime, Harpic?
UPVC cleaner - Ciff, Wilkinsons Astonish,Doctor Power