I had polyhydramnios with my last baby. It was spotted on a growth scan. I don't remember exactly when, but probably 30-32 weeks. I then had to have scans every two weeks. I
The only thing I noticed was that I felt very heavy and uncomfortable because of the amount of fluid in there. I don't know whether it's related, but I went into premature labour and had her at just under 36 weeks. But - she was absolutely fine. No problems at all.
Personally, I think the sheer weight and volume of fluid did make me go into labour because I'm quite petite and I don't think there was any more room in my tummy. When my waters were broken in labour, a huge amount came out!
Don't panic. It's not an uncommon condition with diabetes. It was something they monitored, but they weren't fussing me about it. I was just told they needed to keep an eye on it.
As for the breech, maybe baby has more room to flip about? My current baby was breech a couple of weeks ago but then turned. If you go on all fours or kneel on the floor and lean forward onto the sofa it can help them turn. My midwife said they don't start worrying unless baby is still breech at 36 weeks.
Keep calm *hugs* Do what your team say and watch your blood sugars closely. I'm sure everything will be fine : )