Lucozade staining is very difficult if not near impossible to remove.
Over the years I have cleaned loads of these stains and only ever been able to sucessfully remove one stain permanenly.
Lucozade ingredients: Carbonated water, Glucose Syrup (26%), Citric Acid, Lactic Acid, Flavourings (including Caffeine), Preservatives (Sodium Benzoate, Sodium Bisulphite), Antioxidant (Ascorbic Acid), Colour (Sunset Yellow).
It does not contain any Tannins and the Caffeine % is miniscule.
The problem with the staining blongs to the Sunset yellow food dye/colouring that is used in the drink, that along with the preservatives in the drink usually set the stain in on contact.
I always tell my customers it is in for good as is usaually the case.