LONG scaffolding boards (Sandfields SA12)

I am looking for 4 long scaffolding boards please. I need to replace the flashing on my conservatory roof but it is polypropylene so cannot take any great weight. I thought if I could get 4 scaffolding boards I could put 2 across the roof and 2 laying across these to give a bit more strength so that a worker could get up there and replace the flashing, hope this makes sense ?? Thank you in anticipation.