It could be some sort of horse fly (we don't get true Botflies here). It's bigger than the typical horse botfly that I normally see and the mouth parts are different to a stable fly.

Haven't found anything close to it on various nature photography sites yet. It's likely to be something that's fairly local to my area, which makes it harder to find info.

Definitely a fly. The cicadas we have are significantly bigger than this one, and they hold their wings differently (in a V shape rather than flat).