There isn't much you can do about that on consumer hardware.

We get DDoS’d all the time at work, and we have special appliances that use algorithms to intercept that kind of traffic and absorb it before it hits our production hardware.

When you say UDP Flood attacks, are you actually being flooded to the point you are having problems? Or is it just that you see a lot of packets hitting your FW?

I'm not sure but perhaps Suricata could help in this regard, and identify and simply drop packets from the sites in question?