I have exactly the same issues.
Ever since they have bought out the update, there has been nothing but buffering.
I have checked my Anti-Virus and firewall, turned them off. Reset my router, performed virus scans and cleaned out my cookies and history from my webbrouser, my internet speed is 80mbps, so for the life of me, I guess it is a glitch in the App, of which Sky seem to not want to do anything.
Not to mention that now it automatically conects to my Sky Q box, of which there is no option to stop it from doing that!
Why can't people either leave things alone or prior to bringing new so called improved updates, at least have them tested in real life situations and not some static envirnment?
The old version worked just fine!