Think I may have solved the missing texture issues after reloading a saved game in and around Megaton....plugins...I had 207 active plugins, and after reading a post similar to mine on the forums, I decided to merge a few plugins (the ones recommended in the guide) and so far so good. I hadn't merged them previously because I've never had to in the past but I guess the guide as grown a bit since I last modded FO3 (got bored after playing FO4 for a while! ).
I am, however, still experiencing crashes after reloading a save game. Strangely, I can tell when this is about to happen as I seem to get sudden frame drops and stuttering then it will crash either by freezing on screen or when using doors between areas (exiting or entering Megaton, Super Duper Mart etc.) It seems, at the moment, my only safe bet to reload a save game is to quit the game and reload using the save I want to reload. A bit laborious I know, especially when reloading from dying, but until I've played around a bit more and found a solution, I guess I'll live with it for the time being.
Any help from anyone regarding this would be much appreciated.