Ok, well just figured it out by the looks of it.
If it couldn't resolve DNS for the MiCollab correctly then it bombed out, but didn't tell you that on the ICW or in the logs. All the DNS records had been configured, but initially I pointed the system to 8.8.8.8 during the intial text based setup so that it would licence (as at that stage the server didn't have a route to the DNS Server), and then in the ICW I set the DNS to the internal addres, but it ignored that and continued to use 8.8.8.8.
Logging in to the server manager, setting the DNS server to the internal one (along with the route to that network), and then re-running the ICW seems to have got it past the issue.