Sedge, san pedro and peyote(mescaline containing catus) are both legal in the UK as far as I'm aware so you shouldn't have problems with availability, just pick some up in a smoke shop or online, theres loads of recipes and methods for eating the cactus online (probably a good few on this site alone in the cacti forum) and theres plenty of extraction methods online or in books if you are looking for pure(ish) mescaline.
tastes nasty is a gross understatement. Associate the taste with the impending trip and remind yourself it is for a good cause, you suffer for the end result. I had a HORRIBLE time coming to grips with the flavor of most hallucinogenic mushrooms, but after some training and conditioning, it subsided and the same with torch or pedro, a necessary evil the taste is...
