bcfc
Its been a few years since i did a gft, but you are certain to be asked to stall or two and do a pfl (and steep turns too), as well as some circuit work (likely to include a flapless approach and landing.)
When asked to stall, remember your HASELL check - my examiner asked me to stall over a power station at 2500' I respectfully declined!
On the PFL, just do your best to "get in" to the field, control your glide airspeed tightly (BURN the number into your brain!) and fly as accurately and smoothly as you can.
The same with the steep turns and circuits.
And most important of all .... they are not expect you to be a Concorde pilot, just looking to ensure that you are safe to enjoy your PPL.
Best of luck and the GFT really isn't anything to worry about - you've already made the grade in your lessons, or they wouldn't be putting you up for the test, so just relax and fly to your normal standard.
Let us know how you get on.
Cheers
F3G