In my previous home we had Broadworks. If you search AAM you will see what I have had to say about them.
They are pretty much forcing you to use one supplier (the alternative is to use 'rabbit ears' or go without TV). Dishes are more than likely forbidden by the management/leasehold agreement and may be removed if erected. If Broadworks have exclusive cable rights to the site, then NTL won't/can't provide service. If/when the developer hands over the site, the residents can request NTL to provide cable. I think that other residents contacted the Competition Authority on the issue, but I'm not sure if they got anywhere.