I didn't see an OB until after 12wks, i saw my GP to get the PG confirmed and they gave me the referral dertails to the hospital.
I didn't have a dating scan but i did go t emergency with a bleed at around 6wks, i saw my GP after that and only saw the OB after having appts with the MW.

I don't think there is a real NEED unless your maybe trying to book in with someone with a high demand and basically just getting in as quickly as you can.