I am aware of these ups and downs, but this time this seems like a bigger problem is in the works. I've managed partially to obtain at least some updates to pass through, ie I receive less than 15 freshclam failures daily, by using the gr mirror. However, this is in stark contrast to the stability I have had: less than one failure in 3-6 months...
As for a local mirror: I have a single SME server running, helping a couple of admins on their own systems. So I'd like to avoid the overhead of maintaining another critical infrastructure component.
All in all, it's not a big problem since I am unable to use the unofficial ClamAV updates that would improve detection a lot, so the clients' AV does all the work here.