Having said that, if you live in the Bristol area my dispensary, Urban Fringe is striving to make sure herbs and prepared medicines are still available. Elsewhere you can get a list of practising herbalists from the National Institute of Medical Herbalists and the College of Practitioners of Phytotherapy. Local herbalist will either be able to supply you themselves, or will be able to recommend someone locally.
Of course, you can always try growing some useful herbs yourself, or find places in the wild where you can sustainably harvest them. To learn more about how to identify herbs, and their uses you could do worse than sign up for the urban fringe newsletter below, which will let you know where and when herb walks and other teaching events are taking place.