Cowboy will writers in the UK: Save now and pay later?

In the UK there is apparently a will-writing industry, with non-lawyers in the business of writing wills for people. Usually the customers who use these businesses do so because they are trying to save money, as these businesses are cheaper than lawyers. Apparently there is a reason why they are cheaper, and this article from Diane A. Vieria explains how customers are running into serious problems. We don't have independent will-writers here, but this article really does show how dangerous they can be.