For anyone who is interested - I've just had an email. No code needed - Order by 2nd December and they will upgrade your bottle to the next size up. It doesn't say what happens if you order 100ml because by their logic that should amount to a free bottle, (!!) but I've just ordered a 50ml and will get a 100ml
It's given me the kick up the bum I've needed as I've been meaning to get a bottle of Shazam for a while now. 