September weather will be fine and also depends on the type of transport you take in the route that will make your journey comfy.However Jammu to Srinagar can will take approx 5000 bucks one way.
I can guide you a bit on tht sector,we will discuss this on Sunday.
But your ETA for return train at Uhp from reachin UHP and Srinagar travel is a day less than ideal.