Still mulling over the Forest Gardening course I went on recently in conjunction with re-reading Martin Crawford's excellent book "Creating a Forest Garden". He notes that an "underplanted orchard" is a form of forest gardening i.e. a two-storey approach.
 The UK has a long tradition of orchards and fruit trees so perhaps this could be particularly applicable here; a crossover between horticulture in the traditional sense and permaculture.