I have been prescribed crestor (rosuvastatin) 10mg by my gp for high cholesterol, meanwhile am taking ginkgo biloba as a supplement. Is it safe to?

Most likely. I am not aware of any interaction, running the two through a drug interaction checker yielded this result: 0 interactions found for the drugs you entered. This does not mean no interactions exist, however. Please consult a healthcare professional if you have health concerns.