17 of the 25 will face trial. As for the two brothers mentioned in the OP this should not be confused with the actions of the August 8th.
In August a number of people were preparing to board flights to the US. Their goal was to detonate a liquid explosive device on each of the flights.
Lets wait until the evidence is presented in full at their trial then we can determine if we believe the threat was real or not.
Now for the contreversial bit: Bush and his government were advised about the threat of hijack prior to September 11th 2001 but decided for one reason or another best known to them not to follow this up. The British Government however acted in light of 9/11 and 7/7 to prevent any further tragedy - if they hadn't acted who knows what may have happened.