Update on this so far......
Tech 1 (called when modem is working): Everything looks fine with it. It probably is faulty but if I put it straight to visit they will probably question it. Best bet is to bypass router and when it dies again call up before you reboot.
Tech 2 (modem has locked while router is bypassed): We are showing power but no downstream signal. I will reset your connection. It should now be fine.
Tech 3 (Modem has locked while router is back on (firewall shmirewall!): Reboot a few times please. Turn off all your firewalls please. Run directly without the router and with firewall off dor 24 hours if it happens again we we book a replacement.
Phew, why not just accept that it is 4years old and is getting past it for what I am asking it to do.
Wonder how long until the next call. Good job I'm patient today
