The issues will probably be brightness/colours/contrast, as that's what I'm having problems with lately. Any other C/C welcomed.

Yup, those are the main problems. The render seems overcontrasted, making it look too sharp, and the light source is very bright. I don't really know how to help you with that, the only advice I can give is that you shouldn't alter the original colours too much, it usually makes the image look unnatural. It's better to stick to the original colour scheme of the render/background and just adjust it a little bit when necessary.