Hi all!
I am currently rigging a character but the main issue that I am having is that the model has started to ‘clip’ itself as in some of it just isn’t showing up when I rotate it.
It hasn’t been an issue all day but it has randomly started doing it and I don’t know why or how to fix it.
If anyone can please shed some light on this that would be fantastic - thanks so much!
If your model is getting clipped, it’s probably enormous. You can change the clipping distance in the viewport. Hit the N key to open the number panel if you haven’t already and you should see values for viewport clipping. But before you change the clipping distance, look at the model’s dimensions. If it’s a character, you probably don’t want it to be hundreds of meters tall.
If you’re zoomed in very close you can get clipping issues.
As K Horseman said, play with the clipping distance when you see clipping occur and you’ll see whether to increase/decrease the clipping amount.
Another reason for some areas of your mesh not showing properly could be that the normals need reversing, so check that too.
Thanks a lot for your answers guys!
K Horseman, that solved the issue thanks.
And I did scale the model up but it was necessary to do so, for ease of use for the programmer who needs to use the model 
It was mostly the random nature of the clipping which was confusing me - not an issue at all one minute and then a massive issue literally five minutes later (and the scale and everything of the model remained the same).
But as I said before, changing the clipping distance solved the issue- thanks so much for your answers!