If you are going to buy Xenical online as a substitute for your Orlistat treatment, then you would be able to do this as they have the exact same active ingredient and therefore have the same result. Xenical is the branded version of Orlistat and is, therefore, more expensive. A similar example of this is over the counter paracetamol, the branded version is usually more expensive than the generic version but they are the exact same product.
Orlistat capsules start at £21.95 and Xenical capsules start at £24.95.