Thank you so much for your help both. I've already looked at a fair few tutorials online, but never seem to be able to get quite the same pictures they do. I'm sure I was doing something wrong, hence posting the picture here.
Sorry for the confusion @rickwayne, and thank you for being patient with my noob question. I did take multiple photos, each with a 30s exposure. I've attached an example of the original below... I did spend a lot of time processing the image, so I do take your point onboard. I started off with the 'auto' feature on Lightroom and went from there, which is where the green was introduced I think.
Any advice you can provide would be greatly appreciated.