You definitely need to give birth with someone you trust, I think. Can you go in to the birth centre and sit down and have a talk with the midwives? Maybe request one in particular, after meeting them? (Or maybe there are some girls here on BB who have birthed at that centre, and can recommend someone?) A private midwife and a home birth sounds great to me - I am planning a home birth myself, but that is funded by our provincial health insurance here. Otherwise, maybe you can look into having a doula, and she will advocate for you in labour, and help you through the pain. The only thing you should have to worry about in labour is getting that baby out!
You're right - sometimes the hospital doesn't give the best care, and women and babies suffer for it. But you also need to have good prenatal care now, for the health of yourself and your baby. You need to have your BP monitored, and your baby checked on. Can you keep seeing your GP for that, at least for now? (oh and around here, you can have your BP checked at the local pharmacy/chemist. So you can compare numbers, if you are really concerned that they're not telling you the truth. Also, the hospitals here use a digital BP machine, which can print out the information - BP, heart rate, and temperature. If your birth centre has that, you can ask to see the paper.)
I'd say it's not too late to find someone you trust - talk to the girls here from your area and get a recommendation! And as I said, maybe some have birthed at that birth centre - you might be all set for a great experience already! All the best!