Well, I've got it working and here's a KML file for you to explore in Google Earth. When I say 'it' I mean:
1. Extract the data from the Met Office files
2. Check the Normals
3. Calculate anomaly data for all stations
4. Grid data onto 5 degree square portions of globe using algorithm in the HadCRUT3 paper
5. Turn all that into a coloured KML file for display in Google Earth
And here it is (that is the gridded anomaly data for October 2009 with the 1961-1990 average baseline):
For comparison here's the Met Office's higher resolution picture for the same period. Just staring at the two you can see that approximately the same thing is being plotted with western Europe warmer and Scandinavia and central Europe cooler (you can just make out the same cool spot in Scotland on both).
Phew. That was hard work.
I'll release the code once I've convinced myself that it works correctly.