Hi Chris
that’s achievable
I started at 16:9 and lost just under 2 stones in the first 8 weeks without any extra exercise.
Follow the book closely making sure you eat enough fat from full fat dairy and olive oil etc and make sure to drink the 2 to 3 litres of non sugary fluids per day. <-This is important, I can’t stress it enough. Try to keep the complex carbs down, many of us are doing 50g per day, and you should be very close to target by the time your holidays come around.
Best of luck