Hi Calathea; Yes, dosage is critical, but brand is too. Finding an effective brand has been surprisingly difficult for me. I've tried so many, to list them would wear me out, atm. Swanson's has good prices, I don't know what they charge for shipping to UK, but buying in quantity could be economical. Swanson's price for Enzymatic Therapy is good, but each sublingual is only 1mg. But it may be that you will only need a smaller dosage. iherb has good prices, and ships free in US if the amount is over $ 40.00 US. ( they charge more for E.T., but shipping cost may need to be accounted.) As for other brands, I'm unsure. People have been reporting on the jarrows, did it change? thread.