I have started a new thread for you. Please refer to the sticky at the top of the page with instructions on how to open a new thread which we would prefer that you do rather than tack your post onto a 2 1/2 year old thread.
You will probably be put on emergency code (such as BR), meaning the whole of your pay is subject to 20% tax. When you complete an online form (replacement for P46) to establish your current tax position, you will be put on the correct code, which should be 1060L (the first £10,600 of your pay will be tax-free). If you have overpaid tax already, it will be refunded in your next pay packet.