Completely your call, but I thought I'd let you know that the HB group was talking about a lot more than simply giving them your name and the fact you are pg. It's more about having test results, your current health status, health of the baby, etc, on hand in case you are admitted. I've given them all the paperwork I have from both my m/w and all tests (u/s, blood, etc). Plus, I went through their admissions process to be allocated a patient number, same as every other maternity patient.
The HB m/ws recommended it to all of us HBing Mums as making any transfer process much easier. I am also handing over at this stage my birth plan, for them to keep on file. It potentially means a lot less hassle in the unlikely event that I do need to transfer. A little bit of hassle now is giving me peace of mind that we won't have to face extra dramas down the track. I can deal with it and then forget about it, if that makes sense.
Another point is that I'll be taking the baby up to the hospital to have its hearing test done after birth. So it will be handy to be registered there for that reason too.
If you're worried about the reception you'll get as a HBer, I was so pleasantly surprised yesterday at how nice everyone was. The admissions lady was busy telling me that her sister had two HBs and the m/w was very encouraging of my decision. Not a single raised eyebrow or suggestion that I was causing them any difficulty at all. Completely accommodating.