UK education ranked second in Europe

Also, I wouldn't particularly see it as the role of unions to comment.
I think it would be nice to see some comment from the DfE, the Secretary of State, the Schools' Minister and the rest of the press, who are so quick to report anything negative.

SATs and the run up to GCSE / A levels, POGS.
Teachers have no time to comment on anything!

Whatever the reason it's good news.

I am amazed so little has been commentated on this matter by the Teacher's Unions??

Yes that is true; also Timss and Piris are more closely aligned with the cultural norms of the UK. I gather that the next Pisa will include problem solving which again will be more in tune with the strengths of the UK education system.
Interestingly there is a lot of comment around about how some countries are teaching to the Pisa test, which rather seems to defeat the object.

Maybe the Pisa test didn't include higher education as the article you linked does say 'The rankings include higher education as well as international school tests - which boosted the UK's position.'

There's also a comment from Technorati further down in the comments that seems to say the same thing.