My jnstrcutor has already said that my next lesson will be on steep turns if the weather is good or if not so some more time in the circuit building confidence on going solo (also weather depending).
If you have not gone solo, Ex14, why on earth is you instructor doing Ex 15 Advanced Turning? Its not a case of gaining confidence to go solo, its demonstrating to the instructor that you have the ability to do it and cope with any contingencies. Once you have completed you first solo, you have another 2 hours in the circuit before moving on to the out of circuit work.