Hi MummyOfTerrors.. My DS 'dropped' into position at 24 weeks and was 3/5 over the brim at 25 weeks. There was a bit of a concern that I would go into labour early as I was having strong and regular BH at the time also and I had a threatened prem labour at 29 weeks with my DD. DS decided to stay put and grow right down low in my pelvis (which was mighty uncomfortable!) and he wasn't born until 42 weeks! He was engaged for the whole 16 weeks.
Goodluck. I hope for your hips sake that your baby decides to float back out of your pelvis!