What body? Please stick this into the thread for the camera body you have so others can relate their specific experience. And tell us what you were shooting. It looks like stars and some movement of the camera. Try some post processing and increase the contrast several times. But note, in some post processing when contrast is increased, little artifacts exactly like you are showing seem to come up and are visible only on large crop.

As can seen below taken from the same image as above, the same flecks this time on the stone work of the church have the colour of the stone?

This is becoming a problem as I have some long exposure work to do soon

I have literally thousands of these little white flecks.
They only show up on long exposures, the image here is a 100% crop and was a 3 minute exposure using a 10 stop ND filter.

You can see the regular oil spots or dust or whatever, but what are these?