Hi nappy, they are approx £40 ph so £10 is a great deal! I would definitely get a couple of sessions now if you can, then maybe a follow up one in Jan to review your progress.
I don't use a PT anymore, but I did for a while a few years ago. I think once you get used to weight training you can feel if you are doing it correctly, the important stuff is keeping your core stable, knees don't go beyond toes during squats/lunges. Stop your reps when you feel you are losing good form. There are plenty of great websites to show you new exercises when you want to get specific results or just change things about over time.