The foam is being installed by a company called "tank tigers"
http://www.aoginc.com/ I understand they have a good name but were chosen by Marshall on cost grounds. If the install work is being done against a UOR then the work is on a time and material basis. Given the slow install rate, the RAF could consider "tendering" say 10 airframes to an alternative supplier. I understand the "Twin Peaks" hangar at St Athen is empty, the "Super Hangar" also has capacity and man-power available!
Sir Glenn Torpy seems happy with the rate that the aircraft are being contested. He was also happy to send Hercules to Afghanistan without foam. It is possible to open up a second line, it is just a question of priority. I dispute the comments made by RAF officials in the article above. My own information suggests that all three incidents could be fuel tank explosions. As for XV179 not surviving with foam, it is doubtful any expert could say that with 100% certainty. I do know, USAF Hercules hace survived much worse attacks, but hey, they had fuel tank protection.