Hi, I have a very similar problem with my 7 month DD.
For example, this morning she went to sleep at 9:30am. As she didnt wake herself at 10am at 10:15am I went and opened the curtains. Allowing her to naturally wake up. It was 10:30am and nothing - she was sound asleep. Worried that she wouldn't go down for her Lunchtime nap I opened the tap in the sink which seemed to wake her up (the sound of running water wakes her up).
This afternoon she had a 1 hour nap from 2 till 3. Fingers crossed she is ready for bed by 7!.
I share your same dilemma, to wake or not to wake.
R