I grew up in that part of the world and crossing the Stanwell New Road at 350 feet would be standard to good for a 747-100 in the summer and a Trident full and on a hot day wasn't going upwards very fast either.
it does however seem odd that no one from the airport side of things seem to notice it taking off from a point that is quite long way down the runway. As for the locals complaining well one thing about living that close to an airport you sure as anything pick up on any unusual noise be it louder or different to what you hear all day every day and Stanwell Moor residents would certainly detect that as quick as a flash.