Unfortunately, it is illegal to send medical marijuana products to the UK. Not only is it illegal to ship cannabis products of any kind outside of the U.S., it is also a federal crime to mail them across state lines.
In 2006, the UK legalized one medical marijuana product, Sativex, which treats the symptoms of Multiple Sclerosis. Outside of that, the country has no medical marijuana program. That may soon change, however, as the MHRA, which regulates medicines, has already approved products containing cannabidiol (CBD) for prescription use.