You are ignoring the fact that short term trends change quite rapidly.
Using HadCrut3, for example, the 10 year trends have the following sequence.
0.29
0.25
0.28
0.35
0.33
0.29
0.24
0.24
0.09
0.04
0.07
0.03
-0.03
-0.10
That’s going from 1989-1999 inclusive at the top, to 2004-2011 inclusive, at the bottom. You might like to play with the spreadsheet I’ve made available at SkyDragon to do these calculations quickly.
Swings around a bit, doesn’t it? That’s why we DON’T use the 10 year trend as you have done. That’s why it’s just silly to say Met Office is trying to make us believe what isn’t “actually” the case. The Met Office, after all, specified the time span. What they actually said is (via Leake’s article) is this:
“Our records for the past 15 years suggest the world has warmed by about 0.051C over that period,”
Why would you pick a short term, which is even LESS reliable as an indicator of what’s coming, as what is “actually” happening now? I call BS on that. (BS being “Bad Science”, of course. 
What’s “actually” happening isn’t a trend over any window. Next year might be warmer or cooler; the changes “now” aren’t given by ANY trend. The trend over a window is a diagnostic, used for testing hypotheses. What is ACTUALLY happening now is that the atmospheric greenhouse effect is getting stronger; and at the same time the circulations of water and air and heat and cloud and so on around the globe are going on their merry chaotic way, meaning that we are going to have unpredictable short term variations while there is a continual flow of heat into the ocean from the energy imbalance between what is being emitted and what is being absorbed.
It’s the physics that matters. The behaviour of temperature, along with a lot of other observations, is all backing up the general picture of the planet shifting climate to get into balance with the new atmospheric composition. It’s not just extrapolating trends. It’s classic conventional science, digging into material causes, and forming and testing hypotheses.