Seems like OFGEM have let the cat out the bag!
Checking their website for updates, we came across the new table for after April 1st 2012.
You can download it HERE
Additional note from us 25th Feb, we see the OFGEM chart has been changed from the version seen prompting this post. The text at the top of the document has been added.
Amongst other things, for under 4kW systems, it indicates the new rate will be 45.4p for original 43p system owners. Also indicates that systems installed before 3rd March 2012 will be on the higher rate (43p now then to 45.4p).
Of course this may be a little error. But more likely its the official annoucement dropping in under the radar.