I have located a low cost fleece available from a well known DIY chain in the UK which can also be used to prevent sun scorch. I have put up two layers of fleece and secured them with the same clips used to secure bubble wrap insulation film for winter protection of plants. The two layers of white fleece have had the effect of dispersing and scattering the suns rays inside the greenhouse preventing the direct rays hitting the plants.
For just a few pounds this solution will hopefully help to avoid damage to a large number of young tender plants. I have sufficient fleece left over to provide another two layers of protection if required.