OK done a little more digging, set up a port monitor to look at connections.
As well as the ports listed above iTunes also appear to talk on another couple of ranges, tcp 57345-57370 and tcp 57418-57445. These are obviously dynamic ports and at the moment I have opened up the range tcp 57300-57500 and all apears well.
I would like to narrow the port range if possible and I will keep people updated on my findings.
At present though open tcp 57300-57500 appears to have resolved the issue.