As suggested by RAF paraglider instructors last week.
If you see a fast jet / helicopter coming towards you your best course of action is
a) keep turning so that they have a better chance to see you
b) land before they get to you (at least you will be in control of the landing)
As Francis said, they might not change their flight plan but they will try to give a better look out in that area. The RAF method of looking out is excellent so I would choose option a) probably closely followed by b).
If a fast jet has seen you they will climb (hard depending on separation), roll inverted to keep you in sight, and then roll upright and carry on once past your position. They will climb into cloud if necessary, although they won't be able to see you, they will judge when its safe to come back down. I've also seen them do this when I was ridge soaring in a glider at long mynd.
Alternatively, fly higher than 1000' AGL (above ground level) and most military stuff will be below you by a considerable margin (500' +)
Martin
Notification should be at least 2 hours, preferably 4.