The least they could do.
As with the settlements reached with the men who ended up in Guantanamo, the government has accepted no liability for what happened to al-Saadi, also known as Abu Munthir. Both Munthir and Belhaj were senior leaders in the Libyan Islamic Fighting Group, a faction which had close ties to al-Qaida, prior to its dissolution. This association didn't bother us too much when Libya was a sworn enemy, however: according to David Shayler (prior, it must be said, to his espousal of 9/11 conspiracy theories) MI6 funded a failed assassination attempt on Gaddafi by the LIFG. This accepting of no liability is despite it being the most clear-cut case of collusion with an authoritarian state, thanks to the documents discovered by Human Rights Watch, and our knowing full well that any promises sought that the men would not be mistreated were worthless.
It certainly brings into perspective the anger expressed by Blair at how he couldn't deport anyone designated as a "terrorist suspect" to wherever the hell he felt like; no doubt aware of how swiftly those opposed to a new dictatorial ally had been delivered into their grasp, it must have smarted that the likes of Abu Qatada and others kept winning their legal battles. It also remains to be seen whether charges will be brought against anyone involved in these two cases: the Gibson inquiry into rendition was abandoned as a consequence, ostensibly for the reason that the investigation by the Met would have further delayed the hearing of evidence. I'm certainly not holding my breath on that score.
Considering then that Blair has been making such a killing through his work for Kazakhstan, and Straw will presumably be receiving royalties from his memoir, perhaps the pair would like to contribute towards the £2.2m cost to the taxpayer of their handiwork. It's the least they could do for us, and the country's worldwide reputation for human rights, surely?