Forget the petition. I am sure history will show that there was more to the Nimrod decision than just the SDSR. Would it actually have passed the safety case that the MAA was investigating?
The real campaign should be for a replacement MPA - and that probably being a (quite big) UAV as I can see no need for a manned aircraft in that (maritime) role. The manned element is amply provided by the Merlin MPH.