In fact I've now resolved the issue!!! As I could start in safe mode I went into msconfig (through start menu), clicked selective startup and unchecked "load startup items", then in services I checked "hide all microsoft services". Then I unchecked half of the remainder and restarted my computer. If the black screen still happened, I knew one of these checked services was the problem, if the black screen wasn't there I knew it was one of the unchecked services.
So then I just kept on halving the number of services I had checked and restarting, until I found the culprit that was causing the problem. For me it was AVG antivirus.
Hope this is remotely understandable and useful for anyone else in the same predicament!