It seems like only yesterday you were asking how to get started. Well done for getting where you are so quickly and whatever happens in the next couple of weeks, pat yourself on the back for getting so far.
As for the GFT, I lapsed for 10 years and so I have done two. Both were a doddle, the examiners were both extremely professional but both WANTED me to pass. SAFE flying is the key. Remember that if you pass, you will have been the Captain of the flight. This is a new experience as every time you have flown someone before, you have been a student. It is as well to start your flying as you wish to continue, so as Captain, YOU make all of the decisions. If that means saying “the weather is a bit marginal, I propose we wait for n-time to allow this front to go through” then say it. If he/she passes you, you will have to make that decision every time you fly.
The main difference between the flying you have done up until now, and the GFT, is the GFT is a test and a pressure situation. If you feel under too much stress during the flight, ask the examiner to take control for a couple of minutes and unwind, wipe the sweat from your hands and brow, then when you feel ready, resume control.
Best of Luck Andy, I hope you enjoy the experience.