You can complain here, but I'm not sure what good it will do.
http://www.mod.uk/DefenceInternet/AboutDefence /WhatWeDo/AirSafetyandAviation/LowFlying/HowDo IComplainAboutMilitaryLowFlyingActivity.htm
As I understand it, helicopters (commercial and military) have to stay above 500ft off the ground, and fixed wing aircraft (both types) 2000ft. Or maybe its 3000ft. Either way this doesn't apply to take-off landing zones and it doesn't apply to military aircraft (both types) on exercise. Certain areas of the UK are designated as exercise areas and there are various zones that mean aircraft can do various things in the zones.
To complicate matters further, I believe that Chinooks have to stay at the same height as fixed wing craft because of the hideaous noise they make. Unless apparently they are on exercise. Or just wanting to get home early for a brew.