Hello Jez-
A forum member: "ascpete", and a few others, have done some training using this Japanese method. A search for his past-postings should yield some more information on this subject. You'll spend a few years establishing the basic framework of trunk and branches, and then once this is over, you'll have plenty of figs.
By the way, fig trees are some of the most adaptable-to-training fruit trees that can be grown. Can't speak about the growing conditions in the UK, but I have been growing containerized fig trees since 2007, and training a fig tree is really easy once you establish the basic shape of your tree, be it a Japanese style, many stemmed bush, or, a simple, standard, tree-form. The first 2-4 years should be spent establishing the style and branch structure. Then in the following years, concentrate your efforts on the growing of the branchlets that will bear figs. The more branchlets, and leaves....the more figs. There are past-threads that more thoroughly cover and discuss in detail the pruning methods for production. Training methods used for establishing a basic framework of branches and training for fig production are two different things. Different fertilizers, and different pruning methods.
Go for it. You will do it! Good luck.
Frank