I think Cook and Strauss form a very potent opening combo, and in the absence of KP, England depend heavily on these two to give them a solid start, Cook obviously has some technical issues, but he is by far the best man to open the batting with Strauss.
Then again I raised this point in the 4th test thread, and I say it again, England now aren't really in a position to chop and change much, the likes of Bopara and Bell are heavy run scorers in the CC, and if they fairing so miserably, what are the chances of someone else coming in and doing well.
The fact that the English selectors went back to Bell, despite seeing how awfully he fared during his previous few test matches, kind of indicates the lack of better options.
I have a gut feeling that England aren't going to drop either Bopara or Bell for the 5th test, and the only change could be, Freddie coming in for Harmison.