I couldn't find it locally either, so ordered it from Canada. It arrived quickly (and they emailed me when it was shipped out). I didn't try to find it in capsule form (would probably be under the botanical name of Herba Lysimachiae) since it appears the tincture form works better.
There are several types of Gallstones and not everyone has the calcified ones. I had an ultrasound so I know I have calcified ones that aren't coming out with the flushes. The GCG should break them down so I can flush them out. The fact that the pressure is already better makes me think it really will work.
You might want to contact Julia Chang (the owner) and find out if they ship to UK.