Rory:
Found a little on Dahua I think. (I may have not found the correct site) They do not look much more than a glorified speco product. Limited to combinations of 24 analog/Ip cameras per system. There may be bigger systems, that's just all I found.
Tomcctv/bpzle.
The Aver system mentioned looks good will keep that one in mind if Exacq falls by the wayside Like their predecessor Integral.