We're using the Te Aroha transmitter. Theres a small hill and some trees in the way, so we've moved from a 91 Element antenna to a 43 element one in hope of better signal (less directional). We also have a relatively new (only a year or two old) Hills masthead amplifier.
I was hoping to remove the blockyness im getting on Freeview HD on the HTPC.

At the moment TVNZ is totally unwatchable. TV3 And Kordia seem fine.

Got a signal meter here. Freeview channels:
690.00 - 52dB
698.00 - 38dB
706.25 - 54db

Various UHF analogue channels from scanning
623.25 - 54dB
655.25 - 65dB
671.25 - 55dB
679.25 - 56dB
687.25 - 53dB
751.25 - 62dB
783.25 - 67dB
808.0 - 52dB
858.25 - 50dB
862.25 - 48dB
872.25 - 64dB (i think this is hitting telecom XT here, this is where my signal meter tops out).

So i have no idea whats going on here. This is plenty of signal but its still having issues.