14 lb is almost 3 lb per week!!!! (And that's if you have 5 WI weeks till Christmas - I've only got 4).
I think that you could be pushing it a bit. Not because you aren't in the zone or doing it 100%, but I'm wondering what you are expecting your weekly losses to be?
Sure some people CAN lose quite a bit in their first couple of weeks, but others DON'T. EVERYBODY IS DIFFERENT. Your journey will be YOUR journey.
I don't want to dent your enthusiasm, but I don't want you to be too down-hearted if you don't reach that.
What about aiming for 1/2 a stone first, and then see how long you have left till Christmas.
Good luck. I really hope you can do it.