it looks like you are in New Zealand. If so, options proposed by Americans might not be valid, as your standards and prices may be much different than here (from the technical standpoint). I don't feel comfortable offering advice when I'm not sure if your Telcos offer T-1 (North American standard) or the European E-1 Standard.
I would suggest creating a RFP for the work you need done and bid it out to a couple of small reputable firms, and some larger phone companies. It is their job to create solutions for situations such as yours. Select the bid that seems to provide the best overall solution as relates to your connectivity requirements.