Thanks for your reply... Yes, using an o2 data sim from their VoIP
provider. The APN was set to user mobileweb rather than o2web, which I
have now changed, so waiting to see if that helps.
Did you ever resolve this? I am seeing similar issues with a customer's
D-Link DWR-921 + o2 SIM but, although it does not drop the connection
every day, it usually drops around the same time of day, several times a
week.