I looked into this a number of weeks ago, after getting increasingly frustrated with YouTube on Verizon in the US. I eventually settled on a browser extension (“SmartVideo for YouTube”, for Chrome on Linux) that seems to help. I’m not sure why it helps, to be honest, since it doesn’t actually solve (or even address) the cache-proxy problem, but it definitely helps.
I’m not affiliated with this extension, I’m just a happy customer.
