You are saying Michal, that I should start the programme without a community folder at all and that simply emptying the community folder may not be sufficient?
I have noticed that, since 1.15.7.0 (European update) the black screen events have started to occur almost immediately upon starting the Sim and happen several times throughout the starting sequence. Additionally, yesterday evening I flew a 30 minute flight in the Got Gravel Savage Cub, which had previously seemed immune from trouble but which suffered multiple black screens throughout the flight. Fun when you are 30 feet from touchdown at 35kts, the screen goes black and the stall warning starts chirping away 
It is my suspicion that this is a graphics card problem, more specifically as StopHalfling310 said earlier, a Radeon problem. My next plan is to investigate a clean install of the Radeon card drivers. Not something that I have ever done before. However, I will try your suggestion of renaming the community folder on my next start up and see what happens.
Thanks for your help.
Dave