If you search jobs on this site, Tone Scaffolding in London were looking to recruit and train a Designer. Teeside had posted the job, and i think it came up before. See tonescaffolding.co.uk for contact details.
if your looking to do this stand alone, you'll need a competence in Maths (ie GCSE min pref above), and be willing to work towards engineering qualification (OU is a good place to look). The ability to use Autocad, or simular is a must. Autocad 3d rolls in at a lot £2k, Autocad LT £1k, there are simular, and replicants, but to eventually receive building plans, and send plans to client Autocad is used by a lot.
If you search for Scaffold designers, or Design, it will also give you leads, and Firms who specialise in Cad/Scaffold design
I'd try the Tone route too start, at any rate this will give you an appreciation of what the job would entail, and the qualifications you'd be expected to achieve.
