Can anyone point me towards guidelines for the above, ideally from an authoritive source. It appears to be common practice in the painting and decorating sector to construct a platform in stairwells of houses et . using a leaning ladder, a step ladder and a scaffold board to enable people to access walls in the stairwell, and painters don't like to use brushes or rollers on long poles. There appears to often be no guard rail, or similar, to reduce the risk of persons standing on the platform stepping or falling off the edge of it. I find this approach unsatisfactory, and wondered if anyone could suggest a SENSIBLE way forward.

Virtually all of the larger plant hire companies can supply tower scaffolds for stairwells, it's a very standard item of equipment. Obviously ought to be erected by a PASMA(t) trained person

Dare i say both you and the HSE will find this approach unsatisfactory during an unannounced visit or God forbid, a nasty fall. The things you can get away with in the home whilst doing DIY are not acceptable in the workplace but as Alfasev has indicated, it appears you already know the next step.