For the record, the lunchtime WOL attempt failed 
This was using a python script which sent the packet to the DNS port as that is a UDP port. I used python to get control over the port that was used. There are many reasons it could have failed:
Flaky motherboard/nic/bios/os
Error in python script (it didn't work last night but neither did magic packet).
Port blocked in firewall here
Port blocked by NTL
Port not forwarded correctly by router at home
I should test at home from network, then attempt to test using an old dialup isp account.
Peter's Moblog
