I decided to order two serum kits from Selfridges, in order to cover 2-3 months need. Unfortunately toothpaste was not available this time, hopefully just out of stock? Naturally I was disappointed, because paying 15 £ for shipment every time increases the costs of this trial.
I have now used the toothpaste for two months, and the serum kit three 3-day periods. Do I feel any difference? No. Do I see any difference? May be my teeth are slighly whiter. Or then it just the toilet lighting 😉