Unnamed insect

I found this wee insect on a leaf of our lemon tree. Does anyone know what it is? I thought it may be some member of the fly family, but I'm only guessing.

Got up and milked this morning. Usually it is lovely and cool at 5am, but this morning it was so humid. It was 17 degrees most of the night, which made for really hard sleeping last night. It started to rain during milking, and throughout the morning, but it has now cleared - but is still very humid. It is meant to be again pouring with rain by milking time at 7pm tonight. Lets hope it does, so it will be a lot cooler.